Modern
desktop operating systems are capable of handling large numbers of
different processes at the same time. This screenshot shows Linux Mint running simultaneously Xfce desktop environment, Firefox, a calculator program, the built-in calendar, Vim, GIMP, and VLC media player.
Multitasking capabilities of Microsoft Windows 1.01 released in 1985, here shown running the MS-DOS Executive and Calculator programs
In computing, multitasking is the concurrent execution of multiple tasks (also known as processes)
over a certain period of time. New tasks can interrupt already started
ones before they finish, instead of waiting for them to end. As a
result, a computer executes segments of multiple tasks in an interleaved
manner, while the tasks share common processing resources such as central processing units (CPUs) and main memory.
Multitasking automatically interrupts the running program, saving its
state (partial results, memory contents and computer register contents)
and loading the saved state of another program and transferring control
to it. This "context switch" may be initiated at fixed time intervals (pre-emptive multitasking), or the running program may be coded to signal to the supervisory software when it can be interrupted (cooperative multitasking).
Multitasking does not require parallel execution of multiple tasks at exactly the same time; instead, it allows more than one task to advance over a given period of time. Even on multiprocessor computers, multitasking allows many more tasks to be run than there are CPUs.
Multitasking is a common feature of computer operating systems.
It allows more efficient use of the computer hardware; where a program
is waiting for some external event such as a user input or an input/output transfer with a peripheral to complete, the central processor can still be used with another program. In a time-sharing
system, multiple human operators use the same processor as if it was
dedicated to their use, while behind the scenes the computer is serving
many users by multitasking their individual programs. In multiprogramming systems, a task runs until it must wait for an external event or until the operating system's scheduler forcibly swaps the running task out of the CPU. Real-time
systems such as those designed to control industrial robots, require
timely processing; a single processor might be shared between
calculations of machine movement, communications, and user interface.
Often multitasking operating systems include measures to change
the priority of individual tasks, so that important jobs receive more
processor time than those considered less significant. Depending on the
operating system, a task might be as large as an entire application
program, or might be made up of smaller threads that carry out portions of the overall program.
A processor intended for use with multitasking operating systems
may include special hardware to securely support multiple tasks, such as
memory protection, and protection rings that ensure the supervisory software cannot be damaged or subverted by user-mode program errors.
The term "multitasking" has become an international term, as the
same word is used in many other languages such as German, Italian,
Dutch, Danish and Norwegian.
Multiprogramming
In the early days of computing, CPU time was expensive, and peripherals
were very slow. When the computer ran a program that needed access to a
peripheral, the central processing unit (CPU) would have to stop
executing program instructions while the peripheral processed the data.
This was usually very inefficient.
The first computer using a multiprogramming system was the British Leo III owned by J. Lyons and Co. During batch processing,
several different programs were loaded in the computer memory, and the
first one began to run. When the first program reached an instruction
waiting for a peripheral, the context of this program was stored away,
and the second program in memory was given a chance to run. The process
continued until all programs finished running.
The use of multiprogramming was enhanced by the arrival of virtual memory and virtual machine
technology, which enabled individual programs to make use of memory and
operating system resources as if other concurrently running programs
were, for all practical purposes, nonexistent.
Multiprogramming gives no guarantee that a program will run in a
timely manner. Indeed, the first program may very well run for hours
without needing access to a peripheral. As there were no users waiting
at an interactive terminal, this was no problem: users handed in a deck
of punched cards to an operator, and came back a few hours later for
printed results. Multiprogramming greatly reduced wait times when
multiple batches were being processed.
Cooperative multitasking
Early multitasking systems used applications that voluntarily ceded
time to one another. This approach, which was eventually supported by
many computer operating systems,
is known today as cooperative multitasking. Although it is now rarely
used in larger systems except for specific applications such as CICS or the JES2 subsystem, cooperative multitasking was once the only scheduling scheme employed by Microsoft Windows and Classic Mac OS to enable multiple applications to run simultaneously. Cooperative multitasking is still used today on RISC OS systems.
As a cooperatively multitasked system relies on each process
regularly giving up time to other processes on the system, one poorly
designed program can consume all of the CPU time for itself, either by
performing extensive calculations or by busy waiting; both would cause the whole system to hang. In a server environment, this is a hazard that makes the entire environment unacceptably fragile.
Preemptive multitasking
Preemptive multitasking allows the computer system to more reliably
guarantee to each process a regular "slice" of operating time. It also
allows the system to deal rapidly with important external events like
incoming data, which might require the immediate attention of one or
another process. Operating systems were developed to take advantage of
these hardware capabilities and run multiple processes preemptively.
Preemptive multitasking was implemented in the PDP-6 Monitor and MULTICS in 1964, in OS/360 MFT in 1967, and in Unix in 1969, and was available in some operating systems for computers as small as DEC's PDP-8; it is a core feature of all Unix-like operating systems, such as Linux, Solaris and BSD with its derivatives, as well as modern versions of Windows.
At any specific time, processes can be grouped into two categories: those that are waiting for input or output (called "I/O bound"), and those that are fully utilizing the CPU ("CPU bound"). In primitive systems, the software would often "poll", or "busywait"
while waiting for requested input (such as disk, keyboard or network
input). During this time, the system was not performing useful work.
With the advent of interrupts and preemptive multitasking, I/O bound
processes could be "blocked", or put on hold, pending the arrival of the
necessary data, allowing other processes to utilize the CPU. As the
arrival of the requested data would generate an interrupt, blocked
processes could be guaranteed a timely return to execution.
The earliest preemptive multitasking OS available to home users was Sinclair QDOS on the Sinclair QL, released in 1984, but very few people bought the machine. Commodore's Amiga,
released the following year, was the first commercially successful home
computer to use the technology, and its multimedia abilities make it a
clear ancestor of contemporary multitasking personal computers. Microsoft made preemptive multitasking a core feature of their flagship operating system in the early 1990s when developing Windows NT 3.1 and then Windows 95. It was later adopted on the Apple Macintosh by Mac OS X that, as a Unix-like operating system, uses preemptive multitasking for all native applications.
A similar model is used in Windows 9x and the Windows NT family, where native 32-bit applications are multitasked preemptively. 64-bit editions of Windows, both for the x86-64 and Itanium
architectures, no longer support legacy 16-bit applications, and thus
provide preemptive multitasking for all supported applications.
Real time
Another reason for multitasking was in the design of real-time computing
systems, where there are a number of possibly unrelated external
activities needed to be controlled by a single processor system. In such
systems a hierarchical interrupt system is coupled with process
prioritization to ensure that key activities were given a greater share
of available process time.
Multithreading
As
multitasking greatly improved the throughput of computers, programmers
started to implement applications as sets of cooperating processes
(e. g., one process gathering input data, one process processing input
data, one process writing out results on disk). This, however, required
some tools to allow processes to efficiently exchange data.
Threads
were born from the idea that the most efficient way for cooperating
processes to exchange data would be to share their entire memory space.
Thus, threads are effectively processes that run in the same memory
context and share other resources with their parent processes, such as open files. Threads are described as lightweight processes because switching between threads does not involve changing the memory context.
While threads are scheduled preemptively, some operating systems provide a variant to threads, named fibers,
that are scheduled cooperatively. On operating systems that do not
provide fibers, an application may implement its own fibers using
repeated calls to worker functions. Fibers are even more lightweight
than threads, and somewhat easier to program with, although they tend to
lose some or all of the benefits of threads on machines with multiple processors.
Essential to any multitasking system is to safely and effectively
share access to system resources. Access to memory must be strictly
managed to ensure that no process can inadvertently or deliberately read
or write to memory locations outside the process's address space. This
is done for the purpose of general system stability and data integrity,
as well as data security.
In general, memory access management is a responsibility of the
operating system kernel, in combination with hardware mechanisms that
provide supporting functionalities, such as a memory management unit
(MMU). If a process attempts to access a memory location outside its
memory space, the MMU denies the request and signals the kernel to take
appropriate actions; this usually results in forcibly terminating the
offending process. Depending on the software and kernel design and the
specific error in question, the user may receive an access violation
error message such as "segmentation fault".
In a well designed and correctly implemented multitasking system,
a given process can never directly access memory that belongs to
another process. An exception to this rule is in the case of shared
memory; for example, in the System V
inter-process communication mechanism the kernel allocates memory to be
mutually shared by multiple processes. Such features are often used by
database management software such as PostgreSQL.
Inadequate memory protection mechanisms, either due to flaws in
their design or poor implementations, allow for security vulnerabilities
that may be potentially exploited by malicious software.
Memory swapping
Use of a swap file
or swap partition is a way for the operating system to provide more
memory than is physically available by keeping portions of the primary
memory in secondary storage.
While multitasking and memory swapping are two completely unrelated
techniques, they are very often used together, as swapping memory allows
more tasks to be loaded at the same time. Typically, a multitasking
system allows another process to run when the running process hits a
point where it has to wait for some portion of memory to be reloaded
from secondary storage.
Programming
Processes
that are entirely independent are not much trouble to program in a
multitasking environment. Most of the complexity in multitasking systems
comes from the need to share computer resources between tasks and to
synchronize the operation of co-operating tasks.
Various concurrent computing techniques are used to avoid potential problems caused by multiple tasks attempting to access the same resource.
Bigger systems were sometimes built with a central processor(s) and some number of I/O processors, a kind of asymmetric multiprocessing.
Over the years, multitasking systems have been refined. Modern
operating systems generally include detailed mechanisms for prioritizing
processes, while symmetric multiprocessing has introduced new complexities and capabilities.
Mycorrhizae and changing climate refers to the effects of climate change on mycorrhizae, a fungus which forms an endosymbiotic relationship between with a vascular host plant by colonizing its roots, and the effects brought on by climate change.
Climate change is any lasting effect in weather or temperature. It is
important to note that a good indicator of climate change is global warming, though the two are not analogous.
However, temperature plays a very important role in all ecosystems on
Earth, especially those with high counts of mycorrhiza in soil biota.
Mycorrhizae are one of the most widespread symbioses on the
planet, as they form a plant-fungal interaction with nearly eighty
percent of all terrestrial plants.
The resident mycorrhizae benefits from a share of the sugars and carbon
produced during photosynthesis, while the plant effectively accesses
water and other nutrients, such as nitrogen and phosphorus, crucial to
its health. This symbiosis has become so beneficial to terrestrial plants
that some depend entirely on the relationship to sustain themselves in
their respective environments. The fungi are essential to the planet as
most ecosystems, especially those in the Arctic,
are filled with plants that survive with the aid of mycorrhizae.
Because of their importance to a productive ecosystem, understanding
this fungus and its symbioses is currently an active area of scientific
research.
History of mycorrhizae
First wave – Triassic
Mycorrhizae and their related symbioses have been around for millions of years – dating as far back as the Triassic Period (200–250 million years ago) and even older.
While there are still many gaps in the timeline of mycorrhizae, the
oldest known forms of the fungal group can be dated back as far as
450 million years ago or older, where the first wave the eukaryotic fungi came about alongside the evolution of early land plants. There are some later lineages that consisted only of arbuscular mycorrhizae until the early Cretaceous Period
(75–140 million years ago) when the clade began to drastically branch
off into various forms of mycorrhizae, most of which would be
specialized to particular niches, environments, climates, and plants.
However, these lineages are separate from the lineages that other major
types of mycorrhizae derived from. There are essential mycorrhizae that
evolved from other symbioses such as Ascomycota, (which shares a phylum with Basidiomycota, another major mycorrhiza) which evolved to eventually become Ericoid mycorrhizae or Ectomycorrhizae.
Some of the derived families are more complex due to specialized or
multifunctional roots, which were not present in earlier times before Pangaea.
The climate of the environments these groups of mycorrhizae occupied
(which developed on rocky surfaces) were arid, not allowing for much
diversification in life due to fixed niches.
The downside to looking into the history of most fungi and plant
symbioses is that typically, fungi do not preserve very well, so finding
a fungal fossil of more ancient periods is not only difficult, but
offers only specific information about the fungus and the environment in
which it developed.
Second wave – Cretaceous
This
diversification in both plants and mycorrhizae brought about their
second wave of evolution within the Cretaceous period, which introduced
alongside arbuscular mycorrhizae three new types of mycorrhizae: orchid mycorrhizae, ericoid mycorrhizae, and ectomycorrhizae.
The taxonomic diversification of all plants with and without
mycorrhizal symbiosis shows that 71% makes up arbuscular mycorrhizae,
10% makes up Orchidaceae, 2% make up ectomycorrhizae, and 1.4% make up ericoid mycorrhizae.
The defining feature of this wave of evolution was the consistency of
root types (or in other words, the similarities shared between root
types, though characteristically different for individual families or
even species) within the families that allowed for appropriate symbiosis
with the plants of the period. The environments of this period had a radiation of angiosperms,
showing a different reproductive strategy than before and providing
distinct morphological traits for most varieties of plants as opposed to
prior periods and before the K-Pg extinction event.
The climate that allowed for these developments could be described as
relatively warm, leading to higher sea levels and shallow inland bodies
of water.
These areas were occupied mostly by reptiles that fed on animals, and
insects that fed on plants, showing a more complex ecosystem than was
present in the Triassic period
and further pushing evolution in plants and mycorrhizae via
ever-present natural selection. There is plenty of plant evidence to
support most of these findings; however, the information necessary to
form hypotheses regarding the mycorrhizae of the time, as well as other
related symbioses, is incredibly limited as the fossilization of such
individuals is very rare.
Third wave – Paleogene
The third wave of evolutionary diversification began in the Paleogene Period (24–75 million years ago) and is closely linked with change in climate and soil conditions.
The conditions that caused these changes are mostly due to an increase
in disturbed niches and environments and the warming of global
ecosystems, causing a shift in mycorrhizal types in plants within more
complex soils.
This wave consists of lineages of plants with root morphologies that
are often inconsistent with the previously mentioned families from the
second wave.
These would be referred to as "New Complex Root Clades," due to the
complexities that would arise in peculiar environments between
ectomycorrhizal and nonmycorrhizal plants.
While both the second and third waves are linked to climate change, the
defining feature of the third wave is the increased variability within
the families and complexities in plant-fungus associations.
These stretches of diversification were brought about by an initially
hot and humid climate, but became cooler and drier over time, forcing genetic drift.
These three waves are what help divide and organize most of the
mycorrhizae timeline without getting into specific genera and species.
While it is important to mention the distinction of these fungal types
and their differences, it is equally important to recognize their
counterpart plant diversification as well. There are a number of notable
nonmycorrhizal plants that speciate during the Cretaceous Period—while
there was a spread in mycorrhizal plants, there was also a spread in
nonmycorrhizal plants. This all helps play into a clearly picture of the
distribution of plants and their symbiotic fungi over the course of an
Earth's history.
The effect of climate on plants and mycorrhizae
There
are various effects that a changing climate can have on the numerous
species found within an ecosystem. This includes plants and their
symbiotic relations. As it is understood, any particular mycorrhiza is
expected to be both present and abundant in any of its respective niches
so long as the environment can support its growth. However, sustainable
environments are becoming uncommon due to the effects of a warming,
changing climate. It is important to note that the relationship between
the vascular host plant and mycorrhizae is mutualistic.
This means global environmental change first affects the host plant,
which in turn impacts the mycorrhizae in a very similar way.
Essentially, if the host plant experiences environmental stress, this
will be passed along to the mycorrhizae, which could have negative
consequences.
Arbuscular mycorrhizae,
the most common form of mycorrhizae which are widespread "essential
components of soil biota in natural and agricultural ecosystems", are used as a benchmark for the impacts of climate change on mycorrhizae in the following sections.
Increasing temperatures and excess CO2
The
temperature of the globe is steadily rising due to human activity,
where the majority of the blame can be placed on anthropogenic
production of pollutant gases. The most common gas that is produced by
both artificial and natural means is CO2, and its heavy collective concentration in the atmosphere traps a large amount of heat underneath the atmosphere.
The heat affects fungi differently depending on what genus, species or
strain they are; while some fungi suffer at certain temperatures, others
thrive in them.
This depends on which environments the fungi are most often found in.
However, temperature also plays a vital role in availability of water
and nutrients as the hotter climates will have an easier time absorbing
nutrients but are also threatened by denaturation of proteins.
If the soil is dried by excessive heat, the hyphae of the mycorrhizae
as well as the plant root hairs will have far more difficulty obtaining
both water and the nutrients to sustain their interactions.
While temperature may play a key role in fungal and plant growth, there is equally as much dependence on the amount of CO2 that is absorbed. The amount of CO2 within the soil is different from the amount that is in the air; the presence of this CO2
is a vital part of many plant cycles (such as photosynthesis) and due
to the properties of plant-fungus symbiosis taking place in roots,
mycorrhizae are affected as well. When plants are exposed to higher
levels of CO2, they tend to take advantage of it and grow faster.
This also increases the allocation of carbon to the plant's roots
rather than the plant's shoots, which is beneficial to the symbiotic
mycorrhizae.
There is an increase in the amount of space that the roots can occupy
and thus the cycle of trade between the plant and the fungi increases,
showing potential for further growth and taking advantage of the
available resources until the feedback becomes neutral. The allocated CO2
that is provided to the mycorrhizae also allows them to grow at an
increased rate at higher levels, meaning the hyphae of the fungi will
also expand, however the direct benefits seem to cease there in
accordance to the mycorrhizae, alone.
"Despite significant effects on root carbohydrate levels, there were
generally no significant effects on mycorrhizal colonization."
This means that while the plant may grow larger, the mycorrhizae will
grow proportionally larger with the growth of the plant. In other words,
the mycorrhizae's growth is caused by the growth of the plant; the
opposite cannot be proven true even though these environmental factors
affect both the mycorrhizae and the plant. CO2 should not be
thought of as entirely beneficial: its main contribution is to
photosynthetic processes but the plant relies on it while the essential
sugars that the mycorrhizae require can only be provided by the plant;
they cannot be extracted directly from the soils. The effects CO2 has on the environment are detrimental in the long run as it is a vital contributor to the problem of greenhouse gases and loss of territory in which plants and their respective mycorrhizae grow.
Mycorrhizae in Arctic Regions
While
it may seem like a barren landscape, the Arctic is actually home to
huge populations of animals, plants, and fungi. The plants in these
regions depend on their relationship with mycorrhizae, and without it,
would not fare as well as they do in such harsh conditions. In Arctic
regions, nitrogen and water are harder for plants to obtain as the
ground is frozen, which makes mycorrhizae crucial to their fitness,
health, and growth.
Climate change has been recognized to affect Arctic regions more drastically than non-Arctic regions, a process known as Arctic Amplification. There seem to be more positive feedback loopsthan negativeoccurring
in the Arctic as a result of this, which causes faster warming and
further unpredictable change that will affect its ecosystems.
Since mycorrhizae tend to do better in cooler temperatures, warming
could have a detrimental effect on overall health of colonies.
Since these ecosystems offer soil with sparse, easily accessed
nutrients, it is critical for shrubs and other vascular plants to obtain
such nutrients through their symbiosis with mycorrhiza.
If these relationships are placed under too much stress, a positive
feedback loop could occur causing a decrease in the terrestrial plant
and fungi populations because of harsher and potentially drier
environments.
Biogeographic movement of plants and mycorrhizae
"Fungi
may appear to have limited geographical distributions, but dispersal
per se plays no role in determining such distributions."
The limitations of animals and plants is different from that of fungi.
Fungi tend to grow where there are already plants and probably animals
because many of them are symbiotic in nature and the rely on very
specific environments in order to grow. Plants on the other hand must
rely on separate elements in order to spread, like the wind or other
animals, and when seeds are planted the environments must still be
sufficient enough to help them grow.
Arbuscular mycorrhizae are the best example of this as it is found
nearly anywhere where plants are growing in the wild. However, with
changing climate comes change in environments. As climates warm or cool,
plants tend to "move", that is – they exhibit biogeographic movement.
Some habitats no longer remain viable to certain plants but then other
previously hostile environments may become more hospitable to the same
species.
Once again, if a plant occupies an environment where mycorrhizae can
grow and form a symbiosis with the plant, it will likely occur with
seldom exceptions.
Not all fungi can grow in the same places though, distinct types
of fungi are necessary to consider. Even though some fungi can have a
massive area of dispersal, they still succumb to the same barriers that
most species do. Some elevations are too high or too low and limit the
capacity to disperse spores, favoring similar elevation as opposed to an
increase inclining or declining elevation.
Some biomes are too wet or too dry for a plant to not only move to but
grow and survive in, or the fungi that occupy one climate do not
function as efficiently (if at all) in another climate, limiting the
dispersal even more.
There are other factors that will mediate the dispersal of fungi,
creating boundaries that can cause speciation between fungal
communities, such as distance, bodies of water, strength or direction of
wind, even animal interactions There are "structural differences, such
as mushroom height, spore shape and size of the Buller’s drop, that
determine dispersal distances."
Morphological reproductive traits such as these play a big role in
dispersal, and if there is a barrier that isolates or eliminates these,
such as a river or a lack of soil which can support mycorrhizal
interactions due to something like falling pH levels from acid rain,
essential tactics for germination become obsolete as the offspring do
not survive and thus, the population cannot grow or move. Vertical transmission of mycorrhizae does not exist, so to move past these barriers requires alternative means of horizontal transmission.
Endemism in mycorrhizal fungi is due to the limitations of how fungal
species can spread within their respective niches and home ranges,
noticeably widespread within these areas.
While the changing climates keep these fungi from spreading, they
also illustrate essential points. There is a greater degree of phylogenetic
similarities between fungal communities at similar latitudes and they
exhibit just as much similarity between themselves as do plant
communities.
Tracking one species of plant will help narrow down the specific
movement of the mycorrhizae that are commonly associated with the plant
species. Alaskan trees for example tend to move north as climate changes
because tundra regions are becoming more hospitable and allows for
these trees to grow there.
Mycorrhizae will follow but which ones in specific is difficult to
measure. While vegetation above ground is easier to see and varies less
over a larger region, soil contents vary widely within a much smaller
region. This makes it difficult to pinpoint exact movements of
particular fungi which may be in competition with one another, however
these Alaskan trees have obligate endomycorrhizal symbiotes in great
quantities, so accounting for their movement is easier.
The measurements showed that there were varying distributions of not
only the ectomycorrhizal fungi in trees, but the ericoid mycorrhizae,
orchid mychorrhize, and arbuscular mycorrhizae in shrubs and fruit
plants.
They found that of the measurable ectomycorrhizal species richness and
density, "– the colonization of seedlings declines with increased
distance from forest edge for both native and invasive tree species
across fine spatial scales."
Thus, the greatest inhibitor of forest expansion is actually the
mycorrhizae that prioritize a host's growth rather than their
establishment (planting of the seed). The nutrients in the soil cannot
sustain the complete growth of a tree within the perimeters of the
amount of nutrient absorption that a mycorrhizae (that focuses on growth
rather than establishment) will allow.
The mycorrhizae which help a plant's establishment will aid the species
(and in turn themselves) the most, by maintaining a healthy and
balanced intake of nutrients. Species that are moving away from the
equator due to change in climate likely experience the best benefits
when establishing mycorrhizae infect their roots and spread to other
offspring.
Effects on environmental health
CO2
gases are only one of the most common gases to enter the atmosphere and
circulate within several natural cycles essential to the preservation
of life on a daily basis; however, there are a plethora of other harmful
emissions that can be produced by industrial activity. These gaseous molecules negatively affect the phosphorus cycle, carbon cycle,
water cycle, nitrogen cycle, and many others that keep ecosystems in
check. Mycorrhizal fungi can be affected most heavily by the absorption
of unnatural chemicals that can be found in the soils near man-made
facilities such as factories, which give off many pollutants that can
enter the ecosystem through many means, one of the worst being acid
rain, which can precipitate sulfur and nitrogen oxides into the soils
and harm or kill plants in its path.
This is just one example of how extreme the harsh side effects of
pollution can affect the environment, there is evidence that
agricultural activities are also heavily affected by negative human
influences. The advantage of having a mycorrhizal community in an
agricultural setting is that the plants survive and obtain nutrients
from their environment more easily.
These mycorrhizae are indirectly and directly exposed to the same
effects that human activity stresses upon their respective plants; the
most common fungi being arbuscular mycorrhizae – specifically, the
pollutants of the Earth's atmosphere.
The most common industrial air pollutants that are introduced into the atmosphere include, but are not limited to, SO2, NO-x, and O3 molecules.
These gases all negatively impact mycorrhizal and plant development and
growth. The most notable effects that these gases have on the
mycorrhizae include "– a reduction in viable mycorrhizae propagules,
the colonization of roots, degradation in connections between trees,
reduction in the mycorrhizal incidence in trees, and reduction in the enzyme activity of ectomycorrhizal roots." Root growth and mycorrhizal colonization are important to note as these directly influence how well the plant can uptake essential nutrients, affecting how well it survives more so than the other adverse effects.
Changing climates are correlated with the production of air pollutants,
therefore these results are of significance to the understanding of
how, not only mycorrhizae, but their symbiotic plant-host interactions
are affected as well.
The extinction risk of climate change is the risk of species becoming extinct due to the effects of climate change. This may be contributing to Earth's sixth major extinction, also called the Anthropocene or Holocene extinction.
While the past extinctions have been due to primarily volcanic
eruptions and meteorites, this sixth major extinction is attributed to
human behaviors.
Climate change is occurring at an alarming rate: Studies done by the
Intergovernmental Panel on Climate Change (IPCC) show that it is
estimated that the temperature will rise from about 1.4 to 5.5 degrees
Celsius (2.5 to 10 degrees Fahrenheit) within the next century.
These rising rates, to a certain degree, may benefit some regions while
harming others. However, after about 5.4 degrees Fahrenheit of rising
temperature, it will get into harmful climate change.
Efforts have been made such as the Paris Climate Agreement, in attempt
to stop or reduce the effects of a rising temperature, or at least
decrease the number in which the temperature rises. However, even if
this goal is accomplished, it is estimated that about 25% of their
particular animal species will be lost.
A large fraction of both
terrestrial and freshwater species faces increased extinction risk under
projected climate change during and beyond the 21st century, especially
as climate change interacts with other stressors, such as habitat
modification, over-exploitation, pollution, and invasive species.
Extinction risk is increased under all RCP
scenarios, with risk increasing with both magnitude and rate of climate
change. Many species will be unable to track suitable climates under
mid- and high-range rates of climate change during the 21st century.
Lower rates of climate change will pose fewer problems.
— IPCC, 2014
Some predictions of how life would be affected:
Mediterranean Monk Seal: These animals have lost about 60% of their population in the past sixty years.
Miombo Woodlands of South Africa: If the temperature were to rise by
at least 4.5 degrees Celsius, this area would lose about 90% of its
amphibians, 86% of birds, and 80% of mammals.
The Amazon could lose 69 percent of its plant species.
In southwest Australia 89 percent of amphibians could become locally extinct.
60 percent of all species are at risk of localised extinction in Madagascar.
The Fynbos in the Western Cape Region of South Africa, which is
experiencing a drought that has led to water shortages in Cape Town,
could face localized extinctions of a third of its species, many of
which are unique to that region." - WorldWildLife Fund
Temperature increase would affect the amount of rainfall and
therefore the amount of drinking water animals need to survive. It would
affect plant growth and desertification. This would further spread in
other issues including overgrazing and loss of biodiversity.
Extinction risks reported
2004
In one study published in Nature
in 2004 found that between 15 and 37% of 1103 endemic or near-endemic
known plant and animal species will be "committed to extinction" by
2050.
More properly, changes in habitat by 2050 will put them outside the
survival range for the inhabitants, thus committing the species to
extinction.
Other researchers, such as Thuiller et al., Araújo et al., Person et al., Buckley and Roughgarden, and Harte et al. have raised concern regarding uncertainty in Thomas et al.'s projections; some of these studies believe it is an overestimate, others believe the risk could be greater. Thomas et al. replied in Nature
addressing criticisms and concluding "Although further investigation is
needed into each of these areas, it is unlikely to result in
substantially reduced estimates of extinction. Anthropogenic climate change seems set to generate very large numbers of species-level extinctions." On the other hand, Daniel Botkin et al.
state "... global estimates of extinctions due to climate change
(Thomas et al. 2004) may have greatly overestimated the probability of
extinction..."
Mechanistic studies are documenting extinctions due to recent climate change: McLaughlin et al. documented two populations of Bay checkerspot butterfly being threatened by precipitation change. Parmesan states, "Few studies have been conducted at a scale that encompasses an entire species" and McLaughlin et al. agreed "few mechanistic studies have linked extinctions to recent climate change."
2008
In 2008, the white lemuroid possum was reported to be the first known mammal species to be driven extinct by climate change. However, these reports were based on a misunderstanding. One population of these possums in the mountain forests of North Queensland
is severely threatened by climate change as the animals cannot survive
extended temperatures over 30 °C. However, another population 100
kilometres south remains in good health.
2010
The risk of
extinction does need to lead to a demonstrable extinction process to
validate future extinctions attributable to climate change. In a study
led by Barry Sinervo,
a mathematical-biologist at the University of California Santa Cruz,
researchers analyzed observed contemporary extinctions (since dramatic
modern climate warming began in 1975). Results of the study indicate
that climate-forced extinctions of lizard families of the world have
already started. The model is premised on the ecophysiological limits of
an organism being exceeded. In the case of lizards, this occurs when
their preferred body temperature is exceeded in their local environment.
Lizards are ectotherms that regulate body temperature using heat
sources of their local environment (the sun, warm air temperatures, or
warm rocks). Surveys of 200 sites in Mexico showed 24 local extinctions
(= extirpations), of Sceloporus lizards. Using a model developed from
these observed extinctions the researchers surveyed other extinctions
around the world and found that the model predicted those observed
extirpations, thus attributing the extirpations around the world to
climate warming. These models predict that extinctions of the lizard
species around the world will reach 20% by 2080, but up to 40%
extinctions in tropical ecosystems where the lizards are closer to their
ecophysiological limits than lizards in the temperate zone.
2012
According to research published in the January 4, 2012 Proceedings of the Royal Society B
current climate models may be flawed because they overlook two
important factors: the differences in how quickly species relocate and
competition among species. According to the researchers, led by Mark C. Urban,
an ecologist at the University of Connecticut, diversity decreased when
they took these factors into account, and that new communities of
organisms, which do not exist today, emerged. As a result, the rate of
extinctions may be higher than previously projected.
2014
According to research published in the 30 May 2014 issue of Science,
most known species have small ranges, and the numbers of small-ranged
species are increasing quickly. They are geographically concentrated and
are disproportionately likely to be threatened or already extinct.
According to the research, current rates of extinction are three orders
of magnitude higher than the background extinction rate,
and future rates, which depend on many factors, are poised to increase.
Although there has been rapid progress in developing protected areas,
such efforts are not ecologically representative, nor do they optimally
protect biodiversity. In the researchers' view, human activity tends to
destroy critical habitats where species live, warms the planet, and
tends to move species around the planet to places where they don't
belong and where they can come into conflict with human needs (e.g.
causing species to become pests).
According to a long-term study of more than 60 bee species published in the journal Science said that climate change effect drastic declines in the population and diversity of bumblebees across North America and Europe.This
research show that bumblebees are disappearing at rates same as
"consistent with a mass extinction."North America's bumblebee
populations fell by 46% during the two time periods the study used which
is from 1901 to 1974 and from 2000 to 2014.North America's bumblebee
populations fell by 46% because bee populations were hardest hit in
warming southern regions such as Mexico.According to the study, more frequent extreme warm years, which exceeded the species’ historical temperature ranges.
2016
In 2016, the Bramble Cay melomys, which lived on a Great Barrier Reef
island, was reported to probably be the first mammal to become extinct
because of sea level rises due to human-made climate change.
Extinction risks of the Adelie penguin are being reported because of climate change. The Adelie penguin (Pygoscelis adeliae)
species is declining and data analysis done on the breeding colonies is
used to estimate and project future habitat and population
sustainability in relation to warming sea temperatures. By 2060,
one-third of the observed Adelie penguin colony along the West Antarctic
Peninsula (WAP) will be in decline. The Adelie penguins are a
circumpolar species, used to the ranges of Antarctic climate, and
experiencing population decline. Climate model projections predict
sanctuary for the species past 2099. The observed population is
similarly proportional to the species-wide population (one-third of the
observed population is equal to 20% of the species-wide population).
Sex ratios for sea turtles in the Caribbean
are being affected because of climate change. Environmental data were
collected from the annual rainfall and tide temperatures over the course
of 200 years and showed an increase in air temperature (mean of 31.0
degree Celsius). These data were used to relate the decline of the sex
ratios of sea turtles in the North East Caribbean and climate change.
The species of sea turtles include Dermochelys coriacea, Chelonia myads, and Eretmochelys imbricata.
Extinction is a risk for these species as the sex ratio is being
afflicted causing a higher female to male ratio. Projections estimate
the declining rate of male Chelonia myads as 2.4% hatchlings being male by 2030 and 0.4% by 2090.
2019
According to the World Wildlife Fund, the jaguar is already "near threatened" and the loss of food supplies and habitat due to the fires make the situation more critical.
The fires affect water chemistry (such as decreasing the amount
of dissolved oxygen in the water), temperature, and erosion rates, which
in turn affects fish and mammals that depend on fish, such as the giant otter (Pteronura brasiliensis).
2020
The unprecedented fires of the 2019–20 Australian bushfire season
that have swept through 18 million acres (7 million hectares) have
claimed 29 human lives and have stressed Australia's wildlife. Before the fires, only 500 tiny Kangaroo Island dunnarts (Sminthopsis aitkeni) lived on one island; after half the island was burned, it is possible only one has survived. Bramble Cay melomys (Melomys rubicola)
became the first known casualty of human-caused climate change in 2015
due to rising sea levels and repeated storm surges; the greater stick-nest rat (Leporillus conditor) may be next.
Emus (Dromaius novaehollandiae)
are not in danger of total extinction, although they might suffer local
extinctions as a result of bushfires; in northern New South Wales,
coastal emus could be wiped out by fire. The loss of 8,000 koalas (Phascolarctos cinereus) in NSW alone was significant, but the animals are endangered but not functionally extinct.
A February 2020 study found that one-third of all plant and animal species could be extinct by 2070 as a result of climate change.
Climate change has adversely affected both terrestrial and marine ecosystems, and is expected to further affect many ecosystems, including tundra, mangroves, coral reefs, and caves.
Increasing global temperature, more frequent occurrence of extreme
weather, and rising sea level are among some of the effects of climate
change that will have the most significant impact. Some of the possible
consequences of these effects include species decline and extinction,
behavior change within ecosystems, increased prevalence of invasive
species, a shift from forests being carbon sinks to carbon sources,
ocean acidification, disruption of the water cycle, and increased
occurrence of natural disasters, among others.
General
Global warming is likely to affect terrestrial ecoregions. Increasing global temperature means that ecosystems will change; some species are being forced out of their habitats (possibly to extinction) because of changing conditions, while others are flourishing.
Other effects of global warming include lessened snow cover, rising sea
levels, and weather changes, may influence human activities and the ecosystem.
Within the IPCC Fourth Assessment Report, experts assessed the literature on the impacts of climate change on ecosystems. Rosenzweig et al.
(2007) concluded that over the last three decades, human-induced
warming had likely had a discernible influence on many physical and
biological systems (p. 81). Schneider et al. (2007) concluded, with very high confidence, that regional temperature trends had already affected species and ecosystems around the world (p. 792).
They also concluded that climate change would result in the extinction
of many species and a reduction in the diversity of ecosystems (p. 792).
Terrestrial ecosystems and biodiversity: With a warming
of 3 °C, relative to 1990 levels, it is likely that global terrestrial
vegetation would become a net source of carbon (Schneider et al., 2007:792). With high confidence, Schneider et al.
(2007:788) concluded that a global mean temperature increase of around
4 °C (above the 1990-2000 level) by 2100 would lead to major extinctions
around the globe.
Marine ecosystems and biodiversity: With very high confidence, Schneider et al.
(2007:792) concluded that a warming of 2 °C above 1990 levels would
result in mass mortality of coral reefs globally. In addition, several
studies dealing with planktonic organisms and modelling have shown that
temperature plays a transcendental role in marine microbial food webs,
which may have a deep influence on the biological carbon pump of marine
planktonic pelagic and mesopelagic ecosystems.
Freshwater ecosystems: Above about a 4 °C increase in global mean temperature by 2100 (relative to 1990-2000), Schneider et al. (2007:789) concluded, with high confidence, that many freshwater species would become extinct.
Biodiversity
Extinction
Studying the association between Earth climate and extinctions over the past 520 million years, scientists from the University of York
write, "The global temperatures predicted for the coming centuries may
trigger a new ‘mass extinction event’, where over 50 percent of animal
and plant species would be wiped out."
Many of the species at risk are Arctic and Antarctic fauna such as polar bears and emperor penguins. In the Arctic, the waters of Hudson Bay are ice-free for three weeks longer than they were thirty years ago, affecting polar bears, which prefer to hunt on sea ice. Species that rely on cold weather conditions such as gyrfalcons, and snowy owls that prey on lemmings that use the cold winter to their advantage may be negatively affected. Marine invertebrates achieve peak growth at the temperatures they have adapted to, and cold-blooded animals found at high latitudes and altitudes generally grow faster to compensate for the short growing season. Warmer-than-ideal conditions result in higher metabolism and consequent reductions in body size despite increased foraging, which in turn elevates the risk of predation. Indeed, even a slight increase in temperature during development impairs growth efficiency and survival rate in rainbow trout.
Mechanistic studies have documented extinctions due to recent climate change: McLaughlin et al. documented two populations of Bay checkerspot butterfly being threatened by precipitation change.
Parmesan states, "Few studies have been conducted at a scale that encompasses an entire species" and McLaughlin et al. agreed "few mechanistic studies have linked extinctions to recent climate change." Daniel Botkin and other authors in one study believe that projected rates of extinction are overestimated.
Many species of freshwater and saltwater plants and animals are
dependent on glacier-fed waters to ensure a cold water habitat that they
have adapted to. Some species of freshwater fish need cold water to
survive and to reproduce, and this is especially true with salmon and cutthroat trout. Reduced glacier runoff can lead to insufficient stream flow to allow these species to thrive. Ocean krill, a cornerstone species, prefer cold water and are the primary food source for aquatic mammals such as the blue whale. Alterations to the ocean currents, due to increased freshwater inputs from glacier melt, and the potential alterations to thermohaline circulation of the worlds oceans, may affect existing fisheries upon which humans depend as well.
The white lemuroid possum, only found in the Daintree
mountain forests of northern Queensland, may be the first mammal species
to be driven extinct by global warming in Australia. In 2008, the white
possum has not been seen in over three years. The possums cannot
survive extended temperatures over 30 °C (86 °F), which occurred in
2005.
A 27-year study of the largest colony of Magellanic penguins
in the world, published in 2014, found that extreme weather caused by
climate change is responsible for killing 7% of penguin chicks per year
on average, and in some years studied climate change accounted for up to
50% of all chick deaths. Since 1987, the number of breeding pairs in the colony has reduced by 24%.
Furthermore, climate change may disrupt ecological partnerships
among interacting species, via changes on behaviour and phenology, or
via climate niche mismatch The disruption of species-species associations is a potential
consequence of climate-driven movements of each individual species
towards opposite directions
Climate change may, thus, lead to another extinction, more silent and
mostly overlooked: the extinction of species' interactions. As a
consequence of the spatial decoupling of species-species associations, ecosystem services derived from biotic interactions are also at risk from climate niche mismatch.
Behaviour change
Rising temperatures are beginning to have a noticeable impact on birds, and butterflies
have shifted their ranges northward by 200 km in Europe and North
America. The migration range of larger animals may be constrained by
human development. In Britain, spring butterflies are appearing an average of 6 days earlier than two decades ago.
A 2002 article in Nature
surveyed the scientific literature to find recent changes in range or
seasonal behaviour by plant and animal species. Of species showing
recent change, 4 out of 5 shifted their ranges towards the poles or
higher altitudes, creating "refugee species". Frogs were breeding,
flowers blossoming and birds migrating an average 2.3 days earlier each
decade; butterflies, birds and plants moving towards the poles by 6.1 km
per decade. A 2005 study concludes human activity is the cause of the
temperature rise and resultant changing species behaviour, and links
these effects with the predictions of climate models to provide validation for them. Scientists have observed that Antarctic hair grass is colonizing areas of Antarctica where previously their survival range was limited.
Climate change is leading to a mismatch between the snow camouflage of arctic animals such as snowshoe hares with the increasingly snow-free landscape.
Invasive species
Buffelgrass (Cenchrus ciliaris) is an invasive species throughout the world that is pushing out native species.
As the northern forests are a carbon sink,
while dead forests are a major carbon source, the loss of such large
areas of forest has a positive feedback on global warming. In the worst
years, the carbon emission due to beetle infestation of forests in
British Columbia alone approaches that of an average year of forest
fires in all of Canada or five years worth of emissions from that country's transportation sources.
Research suggests that slow-growing trees only are stimulated in growth for a short period under higher CO2 levels, while faster growing plants like liana benefit in the long term. In general, but especially in rainforests,
this means that liana become the prevalent species; and because they
decompose much faster than trees their carbon content is more quickly
returned to the atmosphere. Slow growing trees incorporate atmospheric
carbon for decades.
Wildfires
Healthy and unhealthy forests appear to face an increased risk of forest fires because of the warming climate. The 10-year average of boreal forest burned in North America, after several decades of around 10,000 km2 (2.5 million acres), has increased steadily since 1970 to more than 28,000 km2 (7 million acres) annually.
Though this change may be due in part to changes in forest management
practices, in the western U.S., since 1986, longer, warmer summers have
resulted in a fourfold increase of major wildfires and a sixfold
increase in the area of forest burned, compared to the period from 1970
to 1986. A similar increase in wildfire activity has been reported in
Canada from 1920 to 1999.
Forest fires in Indonesia
have dramatically increased since 1997 as well. These fires are often
actively started to clear forest for agriculture. They can set fire to
the large peat bogs in the region and the CO₂released by these peat bog
fires has been estimated, in an average year, to be 15% of the quantity
of CO₂produced by fossil fuel combustion.
A 2018 study found that trees grow faster due to increased carbon
dioxide levels, however, the trees are also eight to twelve percent
lighter and denser since 1900. The authors note, "Even though a greater
volume of wood is being produced today, it now contains less material
than just a few decades ago."
In 2019 unusually hot and dry weather in parts of the northern
hemisphere caused massive wildfires, from the Mediterranean to – in
particular – the Arctic. Climate change, by rising temperatures and
shifts in precipitation patterns, is amplifying the risk of wildfires
and prolonging their season. The northern part of the world is warming
faster than the planet on average. The average June temperature in the
parts of Siberia, where wildfires are raging, was almost ten degrees
higher than the 1981–2010 average. Temperatures in Alaska reach record
highs of up to 90 °F (32 °C) on 4 July, fuelling fires in the state,
including along the Arctic Circle.
In addition to the direct threat from burning, wildfires cause
air pollution, that can be carried over long distances, affecting air
quality in far away regions. Wildfires also release carbon dioxide
into the atmosphere, contributing to global warming. For example, the
2014 megafires in Canada burned more than 7 million acres of forest,
releasing more than 103 million tonnes of carbon – half as much as all
the plants in Canada typically absorb in an entire year.
Wildfires are common in the northern hemisphere between May and
October, but the latitude, intensity, and the length of the fires, were
particularly unusual. In June 2019, the Copernicus Atmosphere Monitoring
Service (CAMS) has tracked over 100 intense and long-lived wildfires in
the Arctic. In June alone, they emitted 50 megatones of carbon dioxide -
equivalent to Sweden's annual GHG emissions. This is more than was
released by Arctic fires in the same month in the years 2010 - 2018
combined. The fires have been most severe in Alaska and Siberia, where
some cover territory equal to almost 100 000 football pitches. In
Alberta, one fire was bigger than 300 000 pitches. In Alaska alone, CAMS
has registered almost 400 wildfires this year, with new ones igniting
every day. In Canada, smoke from massive wildfires near Ontario are
producing large amounts of air pollution. The heat wave in Europe also
caused wildfires in a number of countries, including Germany, Greece and
Spain. The heat is drying forests and making them more susceptible to
wildfires. Boreal forests are now burning at a rate unseen in at least 10,000 years.
The Arctic region, is particularly sensitive and warming faster
than most other regions. Particles of smoke can land on snow and ice,
causing them to absorb sunlight that it would otherwise reflect,
accelerating the warming. Fires in the Arctic also increase the risk of
permafrost thawing that releases methane - strong greenhouse gas.
Improving forecasting systems is important to solve the problem. In view
of the risks, WMO
has created a Vegetation Fire and Smoke Pollution Warning and Advisory
System for forecasting fires and related impacts and hazards across the
globe. WMO's Global Atmosphere Watch Programme has released a short
video about the issue.
Invasive species
An invasive species is any kind of living organism that is not native to an ecosystem that adversely affects it.
These negative effects can include the extinction of native plants or
animals, biodiversity destruction, and permanent habitat alteration.
Pine forests in British Columbia have been devastated by a pine beetle
infestation, which has expanded unhindered since 1998 at least in part
due to the lack of severe winters since that time; a few days of extreme
cold kill most mountain pine beetles and have kept outbreaks in the
past naturally contained. The infestation, which (by November 2008) has
killed about half of the province's lodgepole pines (33 million acres or
135,000 km2) is an order of magnitude larger than any previously recorded outbreak.
One reason for unprecedented host tree mortality may be due to that the
mountain pine beetles have higher reproductive success in lodgepole
pine trees growing in areas where the trees have not experienced
frequent beetle epidemics, which includes much of the current outbreak
area. In 2007 the outbreak spread, via unusually strong winds, over the continental divide to Alberta. An epidemic also started, be it at a lower rate, in 1999 in Colorado, Wyoming, and Montana. The United States forest service predicts that between 2011 and 2013 virtually all 5 million acres (20,000 km2) of Colorado's lodgepole pine trees over five inches (127 mm) in diameter will be lost.
Taiga
Climate change is having a disproportionate impact on boreal forests, which are warming at a faster rate than the global average. leading to drier conditions in the Taiga, which leads to a whole host of subsequent issues. Climate change has a direct impact on the productivity of the boreal forest, as well as health and regeneration.
As a result of the rapidly changing climate, trees are migrating to
higher latitudes and altitudes (northward), but some species may not be
migrating fast enough to follow their climatic habitat. Moreover, trees within the southern limit of their range may begin to show declines in growth. Drier conditions are also leading to a shift from conifers to aspen in more fire and drought-prone areas.
Assisted migration
Assisted migration, the act of moving plants or animals to a different habitat,
has been proposed as a solution to the above problem. For species that
may not be able to disperse easily, have long generation times or have
small populations, this form of adaptative management and human
intervention may help them survive in this rapidly changing climate.
The assisted migration of North American forests has been discussed and debated by the science community for decades. In the late 2000s and early 2010s, the Canadian provinces of Alberta and British Columbia finally acted and modified their tree reseeding guidelines to account for the northward movement of forest's optimal ranges. British Columbia even gave the green light for the relocation of a single species, the western larch, 1000 km northward.
Mountains
Mountains
cover approximately 25 percent of earth's surface and provide a home to
more than one-tenth of global human population. Changes in global
climate pose a number of potential risks to mountain habitats. Researchers expect that over time, climate change will affect mountain and lowland ecosystems, the frequency and intensity of forest fires, the diversity of wildlife, and the distribution of fresh water.
Studies suggest a warmer climate in the United States would cause
lower-elevation habitats to expand into the higher alpine zone.
Such a shift would encroach on the rare alpine meadows and other
high-altitude habitats. High-elevation plants and animals have limited
space available for new habitat as they move higher on the mountains in
order to adapt to long-term changes in regional climate.
Changes in climate will also affect the depth of the mountains
snowpacks and glaciers. Any changes in their seasonal melting can have
powerful impacts on areas that rely on freshwater runoff
from mountains. Rising temperature may cause snow to melt earlier and
faster in the spring and shift the timing and distribution of runoff.
These changes could affect the availability of freshwater for natural
systems and human uses.
Oceans
Ocean acidification
Estimated
annual mean sea surface anthropogenic dissolved inorganic carbon
concentration for the present day (normalised to year 2002) from the
Global Ocean Data Analysis Project v2 (GLODAPv2) climatology.
Ocean acidification poses a severe threat to the earth's natural process of regulating atmospheric C02 levels, causing a decrease in water's ability to dissolve oxygen and created oxygen-vacant bodies of water called "dead zones." The ocean absorbs up to 55% of atmospheric carbon dioxide, lessoning the effects of climate change. This diffusion of carbon dioxide into seawater results in three acidic molecules: bicarbonate ion (HCO3-), aqueous carbon dioxide (CO2aq), and carbonic acid (H2CO3).
These three compounds increase the ocean's acidity, decreasing its ph
by up to 0.1 per 100ppm (part per million) of atmospheric CO2.
The increase of ocean acidity also decelerates the rate of
calcification in salt water, leading to slower growing reefs which
support a whopping 25% of marine life.
As seen with the great barrier reef, the increase in ocean acidity in
not only killing the coral, but also the wildly diverse population of
marine inhabitants which coral reefs support.
Dissolved oxygen
Another
issue faced by increasing global temperatures is the decrease of the
ocean's ability to dissolve oxygen, one with potentially more severe
consequences than other repercussions of global warming.
Ocean depths between 100 meters and 1,000 meters are known as "oceanic
mid zones" and host a plethora of biologically diverse species, one of
which being zooplankton. Zooplankton feed on smaller organisms such as phytoplankton, which are an integral part of the marine food web.
Phytoplankton perform photosynthesis, receiving energy from light, and
provide sustenance and energy for the larger zooplankton, which provide
sustenance and energy for the even larger fish, and so on up the food
chain.
The increase in oceanic temperatures lowers the ocean's ability to
retain oxygen generated from phytoplankton, and therefore reduces the
amount of bioavailable oxygen that fish and other various marine
wildlife rely on for their survival.
This creates marine dead zones, and the phenomenon has already
generated multiple marine dead zones around the world, as marine
currents effectively "trap" the deoxygenated water.
Algal bloom
Climate change can increase the frequency and the magnitude of algal bloom. In 2019 the biggest Sargassum bloom ever seen created a crisis in the Tourism industry in North America. The event was probably caused by Climate Change and Fertilizers.
Several Caribbean countries, even considered declaring a state of
emergency due to the impact on tourism. The bloom can benefit the marine
life, but, can also block the sunlight necessary for it.
Impact on phytoplankton
Satellite measurement and chlorophyll observations show decline in the number of phytoplankton,
microorganisms that produce half of the earth's oxygen, absorb half of
the world carbon dioxide and serve foundation of the entire marine food
chain. The decline is probably linked to climate change. However, there are some measurements that show increases in the number of phytoplankton.
Coral bleaching
The warming of water lead to bleaching of the corals what can cause serious damage to them. In the Great Barrier Reef,
before 1998 there were not such events. The first event happened in
1998 and after it they begun to occur more and more frequently so in the
years 2016 - 2020 there were 3 of them.
Combined impact
Eventually
the planet will warm to such a degree that the ocean's ability to
dissolve oxygen will no longer exist, resulting in a worldwide dead
zone.
Dead zones, in combination with ocean acidification, will usher in an
era where marine life in most forms will cease to exist, causing a sharp
decline in the amount of oxygen generated through bio carbon
sequestration, perpetuating the cycle.
This disruption to the food chain will cascade upward, thinning out
populations of primary consumers, secondary consumers, tertiary
consumers, etc., as primary consumers being the initial victims of these
phenomenon.
Marine wildlife
The effect of climate change on marine life and mammals is a growing concern. Many of the effects of global warming
are currently unknown due to unpredictability, but many are becoming
increasingly evident today. Some effects are very direct such as loss of habitat,
temperature stress, and exposure to severe weather. Other effects are
more indirect, such as changes in host pathogen associations, changes in
body condition because of predator–prey interaction, changes in
exposure to toxins and CO 2 emissions, and increased human interactions.
Despite the large potential impacts of ocean warming on marine
mammals, the global vulnerability of marine mammals to global warming is
still poorly understood.
It has been generally assumed that the Arctic marine mammals were the
most vulnerable in the face of climate change given the substantial
observed and projected decline in Arctic sea ice cover. However, the
implementation of a trait-based approach on assessment of the
vulnerability of all marine mammals under future global warming has
suggested that the North Pacific Ocean, the Greenland Sea and the
Barents Sea host the species that are most vulnerable to global warming. The North Pacific has already been identified as a hotspot for human threats for marine mammals
and now is also a hotspot of vulnerability to global warming. This
emphasizes that marine mammals in this region will face double jeopardy
from both human activities (e.g., marine traffic, pollution and offshore
oil and gas development) and global warming, with potential additive or
synergetic effect and as a result, these ecosystems face irreversible
consequences for marine ecosystem functioning. Consequently the future conservation plans should therefore focus on these regions.
Fresh water
Disruption to water cycle
The water cycle
Fresh water covers only 0.8% of the Earth's surface, but contains up to 6% of all life on the planet.
However, the impacts climate change deal to its ecosystems are often
overlooked. Very few studies showcase the potential results of climate
change on large-scale ecosystems which are reliant on freshwater, such
as river ecosystems, lake ecosystems, desert ecosystems, etc. However, a
comprehensive study published in 2009 delves into the effects to be
felt by lotic (flowing) and lentic (still) freshwater ecosystems in the
American Northeast. According to the study, persistent rainfall,
typically felt year round, will begin to diminish and rates of
evaporation will increase, resulting in drier summers and more sporadic
periods of precipitation throughout the year.
Additionally, a decrease in snowfall is expected, which leads to less
runoff in the spring when snow thaws and enters the watershed, resulting
in lower-flowing fresh water rivers.
This decrease in snowfall also leads to increased runoff during winter
months, as rainfall cannot permeate the frozen ground usually covered by
water-absorbing snow. These effects on the water cycle will wreak havoc for indigenous species residing in fresh water lakes and streams.
Salt water contamination and cool water species
Eagle River in central Alaska, home to various indigenous freshwater species.
Species of fish living in cold or cool water can see a reduction in
population of up to 50% in the majority of U.S. fresh water streams,
according to most climate change models.
The increase in metabolic demands due to higher water temperatures, in
combination with decreasing amounts of food will be the main
contributors to their decline.
Additionally, many fish species (such as salmon) utilize seasonal water
levels of streams as a means of reproducing, typically breeding when
water flow is high and migrating to the ocean after spawning.
Because snowfall is expected to be reduced due to climate change, water
runoff is expected to decrease which leads to lower flowing streams,
effecting the spawning of millions of salmon.
To add to this, rising seas will begin to flood coastal river systems,
converting them from fresh water habitats to saline environments where
indigenous species will likely perish. In southeast Alaska, the sea
rises by 3.96 cm/year, redepositing sediment in various river channels
and bringing salt water inland.
This rise in sea level not only contaminates streams and rivers with
saline water, but also the reservoirs they are connected to, where
species such as Sockeye Salmon live. Although this species of Salmon can
survive in both salt and fresh water, the loss of a body of fresh water
stops them from reproducing in the spring, as the spawning process
requires fresh water.
Undoubtedly, the loss of fresh water systems of lakes and rivers in
Alaska will result in the imminent demise of the state's once-abundant
population of salmon.
Droughts
Droughts
have been occurring more frequently because of global warming and they
are expected to become more frequent and intense in Africa, southern
Europe, the Middle East, most of the Americas, Australia, and Southeast
Asia.
Their impacts are aggravated because of increased water demand,
population growth, urban expansion, and environmental protection efforts
in many areas. Droughts result in crop failures and the loss of pasture grazing land for livestock.
Droughts are becoming more frequent and intense in arid and
semiarid western North America as temperatures have been rising,
advancing the timing and magnitude of spring snow melt floods and
reducing river flow volume in summer. Direct effects of climate change
include increased heat and water stress, altered crop phenology,
and disrupted symbiotic interactions. These effects may be exacerbated
by climate changes in river flow, and the combined effects are likely to
reduce the abundance of native trees in favor of non-native herbaceous
and drought-tolerant competitors, reduce the habitat quality for many
native animals, and slow litter decomposition and nutrient cycling.
Climate change effects on human water demand and irrigation may
intensify these effects.
Combined impact
In
general, as the planet warms, the amount of fresh water bodies across
the planet decreases, as evaporation rates increase, rain patterns
become more sporadic, and watershed patterns become fragmented,
resulting in less cyclical water flow in river and stream systems. This
disruption to fresh water cycles disrupts the feeding, mating, and
migration patterns of organisms reliant on fresh water ecosystems.
Additionally, the encroachment of saline water into fresh water river
systems endangers indigenous species which can only survive in fresh
water.
Species migration
In 2010, a gray whale
was found in the Mediterranean Sea, even though the species had not
been seen in the North Atlantic Ocean since the 18th century. The whale
is thought to have migrated from the Pacific Ocean via the Arctic.
Climate Change & European Marine Ecosystem Research (CLAMER) has also reported that the Neodenticula seminae
alga has been found in the North Atlantic, where it had gone extinct
nearly 800,000 years ago. The alga has drifted from the Pacific Ocean
through the Arctic, following the reduction in polar ice.
In the Siberian subarctic,
species migration is contributing to another warming albedo-feedback,
as needle-shedding larch trees are being replaced with dark-foliage
evergreen conifers which can absorb some of the solar radiation that
previously reflected off the snowpack beneath the forest canopy. It has been projected many fish species will migrate towards the North
and South poles as a result of climate change, and that many species of
fish near the Equator will go extinct as a result of global warming.
Migratory birds are especially at risk for endangerment due to
the extreme dependability on temperature and air pressure for migration,
foraging, growth, and reproduction. Much research has been done on the
effects of climate change on birds, both for future predictions and for
conservation. The species said to be most at risk for endangerment or
extinction are populations that are not of conservation concern.
It is predicted that a 3.5 degree increase in surface temperature will
occur by year 2100, which could result in between 600 and 900
extinctions, which mainly will occur in the tropical environments.
Species adaptation
In November 2019 it was revealed that a 45-year study indicated that climate change had affected the gene pool of the red deer population on Rùm, one of the Inner Hebrides islands, Scotland.
Warmer temperatures resulted in deer giving birth on average three days
earlier for each decade of the study. The gene which selects for
earlier birth has increased in the population because does with the gene
have more calves over their lifetime. Dr Timothée Bonnet, of the Australian National University, leader of the study, said they had "documented evolution in action".
In December 2019 the results of a joint study by Chicago's Field Museum and the University of Michigan into changes in the morphology of birds was published in Ecology Letters.
The study uses bodies of birds which died as a result of colliding with
buildings in Chicago, Illinois, since 1978. The sample is made up of
over 70,000 specimens from 52 species and span the period from 1978 to
2016. The study shows that the length of birds' lower leg bones (an
indicator of body sizes) shortened by an average of 2.4% and their wings
lengthened by 1.3%. The findings of the study suggest the morphological
changes are the result of climate change, and demonstrate an example of
evolutionary change following Bergmann's rule.
Impacts of species degradation due to climate change on livelihoods
The livelihoods of nature dependent communities depend on abundance and availability of certain species.
Climate change conditions such as increase in atmospheric temperature
and carbon dioxide concentration directly affect availability of biomass
energy, food, fiber and other ecosystem services. Degradation of species supplying such products directly affect the livelihoods of people relying on them more so in Africa. The situation is likely to be exacerbated by changes in rainfall variability which is likely to give dominance to invasive species especially those that are spread across large latitudinal gradients.
The effects that climate change has on both plant and animal species
within certain ecosystems has the ability to directly affect the human
inhabitants who rely on natural resources. Frequently, the extinction of
plant and animal species create a cyclic relationship of species
endangerment in ecosystems which are directly affected by climate
change.
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