North American Cordillera

From Wikipedia, the free encyclopedia

North American Cordillera
The mountainous western part of North America is called a "cordillera".
Highest point
Peak	Denali
Elevation	6,168 m (20,236 ft)
Dimensions
Length	6,400 km (4,000 mi)
Geography
Countries	United States, Canada and Mexico

The North American Cordillera is the North American portion of the American Cordillera which is a mountain chain (cordillera) along the western side of the Americas. The North American Cordillera covers an extensive area of mountain ranges, intermontane basins, and plateaus in western North America, including much of the territory west of the Great Plains. It is also sometimes called the Western Cordillera, the Western Cordillera of North America, or the Pacific Cordillera.

The precise boundaries of this cordillera and its subregions, as well as the names of its various features, may differ depending on the definitions in each country or jurisdiction, and also depending on the scientific field; this cordillera is a particularly prominent subject in the scientific field of physical geography.

Major features

Physiographic divisions of the western United States include three mountain systems: the Rocky Mountain System (areas 16–19), the Cascade–Sierra Mountains (23), and the Pacific Border Province (24).

 

Physiographic divisions of Mexico include three mountain systems: the Sierra Madre Oriental, the Sierra Madre Occidental, and the Sierra Madre del Sur (which is an extension of the Peninsular Ranges).

 

This cordillera extends from the U.S. state of Alaska to the southern border of Mexico. The North American Cordillera includes some of the highest peaks on the continent. Its mountain ranges generally run north to south along three main belts: the Pacific Coast Ranges in the west, the Nevadan belt in the middle (including the Sierra Nevada), and the Laramide belt in the east (including the Rocky Mountains).

These three orogenic belts (also called "orogens") arose due to the engagement of tectonic plates which deformed the Earth's lithosphere (crust and uppermost mantle). For example, the Laramide orogeny changed the topography of the central Rocky Mountains and adjoining Laramide regions (from central Montana to central New Mexico) during the Late Cretaceous 80 million years ago. Prior to this time the Rocky Mountain region was occupied by a broad basin. Further topographical evolution occurred during the Eocene (55–50 million years ago) and Oligocene (34–23 million years ago), but since that time the region has been relatively stable. Generally speaking, it will be convenient here to consider these three belts going west to east, and north to south. 

In Alaska, south of the Interior Plains area, is the Rocky Mountain System, then the Intermontane Basins and Ranges, and in the southern part of the state are the Pacific Mountains and Valleys. In the Alaska panhandle, the mainland mountain ranges and offshore islands (the Alexander Archipelago) are extensions of respective ranges further south.

In Canada, the North American Cordillera is usually divided into three physiographic regions: the western system, the interior system, and the eastern system. The western system includes the Coast Mountains, the interior system includes the Columbia Mountains, and the eastern system includes the Canadian Rockies.

At its midsection between San Francisco, California and Denver, Colorado, the North American Cordillera is about 1,000 miles (1,600 km) wide, and its physiographic provinces at this midpoint are as follows, going from west to east: the Pacific Coast Ranges, the Central Valley, the Sierra Nevada, the Basin and Range Province (forming many narrow ranges and valleys), the Colorado Plateau, and the Rocky Mountains. In the United States, another major feature of the Cordillera is the Columbia Plateau, located north of California between the Cascade Range — which is a northern extension of the Sierra Nevada — and the Rocky Mountains. 

In Mexico, the Sierra Madre Occidental, and the Sierra Madre Oriental further east, surround the Mexican Plateau. To the west of the Sierra Madre Occidental, the Peninsular Ranges border the Pacific Ocean, and the Sierra Madre del Sur is the southern extension of the Peninsular Ranges. Sierra Madre means "Mother Range" in Spanish. 

The Nevadan belt runs up and down the middle of the North American Cordillera. Therefore, the intermontane areas of the cordillera can be divided up into the areas east of the Nevadan belt, and those west of the Nevadan belt.

Pacific Coast Belt

The Pacific Coast Ranges, comprising the Pacific Coast Belt, parallel the North American Pacific Coast, and comprise several mountain systems. Along the British Columbia and Alaska coast, the mountains intermix with the sea in a complex maze of fjords, with thousands of islands. Off the Southern California coast the Channel Islands archipelago of the Santa Monica Mountains extends for 160 miles (260 km).

Southern Alaska ranges

In southern Alaska, the primary mountain ranges are the Alaska Range, Wrangell Mountains, Saint Elias Mountains, Kenai Mountains, Chugach Mountains, and Talkeetna Mountains.

Western System of Canada

Mount Robson in British Columbia

 

The Yukon Ranges comprise the mountains in the southeastern part of the U.S. state of Alaska and most of the Yukon, Canada. This range has an area of 364,710 km² (140,820 sq mi).

The Coast Mountains run from the lower Fraser River and the Fraser Canyon northwestward, separating the Interior Plateau from the Pacific Ocean. Their coastal flank is characterized by an intense network of fjords and associated islands, very similar to the Norwegian coastline, while their inland side against the plateau they transition to the high plateau in dryland valleys notable for a series of large lakes similar to the alpine lakes of southern Switzerland, beginning in deep mountains and ending in flatland. They are subdivided in three main groupings, the Pacific Ranges between the Fraser and Bella Coola, the Kitimat Ranges from there northwards to the Nass River and the Boundary Ranges from there to their terminus in the Yukon Territory at Champagne Pass and Chilkat Pass northwest of Haines, Alaska. The Saint Elias Mountains lie to their west and northwest, while the Yukon Ranges and Yukon Basin lie to their north. On the inland side of the Boundary Ranges are the Tahltan and Tagish Highlands and also the Skeena Mountains, part of the Interior Mountains system, which also extend southwards on the inland side of the Kitimat Ranges.

The terrain of the main spine of the Coast Mountains is typified by heavy glaciation, including several very large icefields of varying elevation. Of the three subdivisions, the Pacific Ranges are the highest and are crowned by Mount Waddington, while the Boundary Ranges contain the largest icefields, the Juneau Icefield being the largest. The Kitimat Ranges are lower and less glacier-covered than either of the other two groupings, but are extremely rugged and dense. 

The Coast Mountains are made of igneous and metamorphic rock from an episode of arc volcanism related to subduction of the Kula and Farallon Plates during the Laramide orogeny about 100 million years ago. The widespread granite forming the Coast Mountains formed when magma intruded and cooled at depth beneath volcanoes of the Coast Range Arc whereas the metamorphic formed when intruding magma heated the surrounding rock to produce schist. 

The Insular Mountains extend from Vancouver Island in the south to the Queen Charlotte Islands in the north on the British Columbia Coast. It contains two main mountain ranges, the Vancouver Island Ranges on Vancouver Island and the Queen Charlotte Mountains on the Queen Charlotte Islands.

Pacific Border Province in contiguous U.S.

Olympic Mountains in Washington

 

The Olympic Mountains is a mountain range on the Olympic Peninsula of western Washington in the United States. The mountains, part of the Pacific Coast Ranges, are not especially high – Mount Olympus is the highest at 7,962 ft (2,427 m) – but the western slopes of the Olympics rise directly out of the Pacific Ocean and are the wettest place in the 48 contiguous states. Most of the mountains are protected within the bounds of the Olympic National Park. 

The Oregon Coast Range is the part of the Coast Range system that is denoted as between the mouth of the Columbia River and the Middle Fork Coquille River. It is about 200 miles (320 km) long. The highest peak is Marys Peak, at 4,101 ft (1,250 m). 

The California Coast Ranges are one of the eleven traditional geomorphic provinces of California. This province includes several – but not all – mountain ranges along the California coast (the Transverse Ranges, Peninsular Ranges and the Klamath Mountains are not included).

Western mountain ranges of Mexico

The Sierra Madre del Sur mountains in southwestern Mexico form a southern extension of the Peninsular Ranges of Baja, California. The Peninsular Ranges are separated from the Sierra Madre del Sur by an expanse of ocean.

Nevadan belt

The Nevadan belt is located between the Pacific coast belt and the Laramide belt. Nevada means "snow-covered" in Spanish.

Interior System of Canada

In Canada, the Northern Interior Mountains are a northern extension of the Columbia Mountains. They include the Hazelton Mountains, Cassiar Mountains, Omineca Mountains, and Skeena Mountains. 

Location map of Columbia Mountains

 

Monashee Mountains

 

The Columbia Mountains are a designation in British Columbia for a group of four ranges lying between the Rocky Mountain Trench (to the east) and the Interior Plateau (to the west). These ranges are the Cariboo Mountains, which are the northernmost and sometimes considered to be part of the Interior Plateau, the Selkirk Mountains, the Purcell Mountains, and the Monashee Mountains. 

The Columbia Mountains are classified as being in Canada's interior system, rather than its eastern system. However, the Columbia Mountains are an extension of mountains in the United States that are considered part of the Rocky Mountains, and therefore the Columbia Mountains are often treated as being part of the Rockies.

The Selkirks and Purcells lie entirely within the basin of the Columbia River, while the Monashees lie to the river's west on its southward course from its Big Bend and are flanked on the west by the basin of the Thompson and Okanagan Rivers. There are many named subranges of all four subgroupings, particularly in the Selkirks and Monashees. The southward extension of the Selkirks, Purcells and Monashees into the United States are reckoned to be part of the Rocky Mountains and the designation Columbia Mountains is not used there (the Purcells, also, go by the name "Percell Mountains" in the United States). The Salish and Cabinet Mountains south of the Kootenai River are essentially part of the same landform, but are officially designated part of the Rocky Mountains in the United States. 

To the west of the Monashees and Cariboos, there are three intermediary upland areas which are transitional between the mountain ranges and the plateaus flanking the Fraser and Thompson Rivers. These – the Quesnel, Shuswap and Okanagan Highlands, are sometimes considered as being part of the neighbouring ranges rather than the plateaus and are often spoken of that way locally but are formally designated as being part of the Interior Plateau. The southernmost extends into the Washington, where it is named by the American spelling Okanogan Highland (and was the first-named of these groupings).

Cascade–Sierra Mountains in contiguous U.S.

The Cascade Range (called the Cascade Mountains in Canada) extends from northern California in the United States to British Columbia, Canada. It consists of non-volcanic and volcanic mountains: all of the known historic eruptions in the contiguous United States have been from the volcanoes of the Cascade Volcanic Arc. The highest peak in the Cascade Range is Mount Rainier (14,409 feet (4,392 m)), a stratovolcano. The small portion of the Cascade Range in Canada is called the Cascade Mountains or Canadian Cascades, and in its southwestern area is similar in terrain to the area north of Glacier Peak, known as the North Cascades, and its northern and eastern extremities verge on the Thompson Plateau in a less rugged fashion than in most other parts of the range. The North Cascades are very different in character from the series of high volcanic stratovolcanoes from Rainier southwards to Mount Shasta and Lassen Peak, and is more severely alpine and steeply rugged, particularly the Skagit Range. Inland portions of the range are dryland and plateau-like in character, e.g. the Okanagan Range, which lies along the Cascades' northeastern margin, separated by the Similkameen River. 

The Sierra Nevada forms an inland mountain spine of northern California, extending from the terminus of the Cascade Range south of Lassen Peak southwards along the east flank of the Central Valley of California to the Transverse Ranges, forming a mountain region of complex terrain and varied geology which separates the Central Valley from the Great Basin to the east. The mean height of the mountain summits in the Sierra Nevada gradually increases from north to south, culminating at Mount Whitney (14,505 feet (4,421 m)), the highest point in the contiguous United States. From east to west, the Sierra is wedge-shaped: the west slope gradually rises and the east slope forms a steep escarpment, particularly so in the southern portion.

The northern Sierra surface rocks are predominantly volcanic, while the southern Sierra granitic batholith has been sculpted by glaciers into dramatic U-shaped valleys and thin ridges called Arêtes.

Sierra Madre Occidental in Mexico

The Sierra Madre Occidental mountain range is a southern extension of the Sierra Nevada. The range extends from near the Arizona border down to the Sierra Madre del Sur, along the western mainland of Mexico. The high plateau that is formed by the range is cut by deep river valleys.

Laramide Belt

The Laramide belt is on the side of the North American Cordillera most distant from the Pacific Coast Ranges. It is named for the Laramie Mountains of eastern Wyoming (in turn named for Jacques La Ramee, a trapper who disappeared in the Laramie Mountains in 1820 and was never heard from again).

Alaska and Eastern System of Canada

The Brooks Range in Alaska

 

The Brooks Range includes the northernmost of the major mountain systems of the North American Cordillera, and extend along an east–west axis across northern Alaska from near the northern opening of the Bering Strait to the northern Yukon Territory. Major subranges include the British Mountains and Richardson Mountains, towards their eastern end, and at their farthest west is the small subrange that De Long Mountains. The Brooks Range forms the northern flank of the lower Yukon River basin, separating it from Alaska's North Slope region, facing the beaufort Sea. The Brooks Range is considered part of (or an extension of) the Rockies. South of the Brooks Range are the Mackenzie Mountains, and the Canadian Rockies.

Rocky Mountain System in contiguous U.S.

In the Rocky Mountains, the highest peak is Mount Elbert in Colorado at 14,439 feet (4,401 m) above sea level. The American Rockies rise steeply over the Interior Plains to the east, and over the Great Basin to the west, and extend south to the Rio Grande in New Mexico. The United States definition of the Rockies includes the Cabinet and Salish Mountains of Idaho and Montana, whereas their counterparts north of the Kootenai River, the Columbia Mountains, are sometimes considered a separate system lying to the west of the huge Rocky Mountain Trench which runs the length of British Columbia.

Sierra Madre Oriental in Mexico

The Sierra Madre Oriental mountains in eastern Mexico are a southern extension of the Rocky Mountains. The Sierra Madre Oriental spans about 1,000 km (600 miles). Mexico's Gulf Coastal Plain lies to the east of the range, between the mountains and the Gulf of Mexico coast. The Mexican Plateau lies to the west of the range.

Intermontane areas seaward from the Nevadan belt

The Nevadan belt runs down the middle of the North American Cordillera. Therefore, the intermontane areas can be divided up into the areas east of the Nevadan belt, and those west of the Nevadan belt.

Canada portion

Interior Plateau

 

Shuswap Highland

 

The Interior Plateau is the northern continuation of the Columbia Plateau, and covers much of inland British Columbia. The Cariboo Mountains and Monashee Mountains lie to the east, the Canadian Cascades are to the southwest, and the Hazelton Mountains and Coast Range to the west and northwest.

Within the Interior plateau, the Shuswap Highland consists of a portion of the foothills between the Thompson Plateau and Bonaparte Plateau on the west, and the Monashee Mountains and Cariboo Mountains on the east and northeast.

Thompson Plateau

 

Okanagan Highland

 

Also within the Interior plateau, the Thompson Plateau forms the southern portion of the Interior Plateau. It is bordered on the south by the Canadian Cascades and on the north by the Thompson River.

The Okanagan Highland is the part of the Interior Plateau to the east of the Thompson Plateau, and is bounded by the Okanagan River on the west, the Shuswap River on the north, and the Kettle River on the east side. The Okanagan Highland is described as being a hilly plateau, and is located in southern British Columbia and northern Washington. The Interior Plateau also includes the Quesnel Highland, Fraser Plateau, Nechako Plateau, and McGregor Plateau.

Portion in contiguous U.S.

California's Central Valley is a large, flat valley that dominates the central portion of California, stretching inland and parallel to the Pacific Ocean coast. Its northern half is referred to as the Sacramento Valley, and its southern half as the San Joaquin Valley. The two halves meet at the huge Sacramento-San Joaquin River Delta of the Sacramento and San Joaquin Rivers, which along with their tributaries drain the majority of the valley. The Central Valley covers an area of approximately 22,500 square miles (58,000 km²), making it slightly smaller than the state of West Virginia and about 13.7% of California's total area. The Central Valley is 40 to 60 miles (60 to 100 km) wide, with the Sierra Nevada to the east and the Coast Ranges to the west.

Mexican portion

The Gulf of California is a body of water that separates the Peninsular Ranges from the Sierra Madre Occidental on the Mexican mainland. The Gulf of California is 1,126 km (700 miles) long and 48 to 241 km (30 to 150 miles) wide, with an area of 177,000 km² (68,000 sq mi), a mean depth of 818.08 m (2,684.0 ft), and a volume of 145,000 km³ (35,000 cu mi).

Intermontane areas inland from the Nevadan belt

Canadian portion

The Rocky Mountain Trench is a large valley that extends approximately 1,600 km (990 mi) from Flathead Lake, Montana, to the Liard River, just south of the British Columbia–Yukon border near Watson Lake, Yukon. The trench bottom is 3 to 16 km (2 to 10 miles) wide and ranges from 600 to 900 m (2,000 to 3,000 ft) above sea level. The general orientation of the Trench is almost uniformly pointing north. Some of its topography has been carved into glacial valleys, but it is primarily a byproduct of faulting. The Trench separates the Rocky Mountains on its east from the Columbia Mountains and the Cassiar Mountains on its west. It is up to 25 km (16 miles) wide, if measured peak-to-peak. 

For convenience the Rocky Mountain Trench may be divided into northern and southern sections. The dividing point reflects the separation of north and easterly flows to the Arctic Ocean versus south and westerly flows to the Pacific Ocean. A break in the valley system at around 54°N near Prince George, British Columbia may be used for this purpose. There are three main mountain ranges in the Canadian area named the Rocky Mountains, the Columbia Mountains, and the Coast Mountains.

Portion in contiguous U.S.

Colorado Plateau

 

Basin & Range Province (indicated in blue)

 

The Columbia Plateau is a geologic and geographic region that lies across parts of the U.S. states of Washington, Oregon, and Idaho. It is a wide flood basalt plateau between the Cascade Range and the Rocky Mountains, cut through by the Columbia River. In one of various usages, the term "Columbia Basin" refers to more or less the same area as the Columbia Plateau.

The Basin and Range province covers most of the state of Nevada and parts of the states of Arizona, California, Idaho, New Mexico, Oregon, Texas, Utah, and Wyoming, as well as much of northern Mexico. It is an extremely arid region characterized by basin and range topography.

The Colorado Plateau is an area of high desert located in Arizona, New Mexico, Colorado, and Utah, bisected by the Colorado River which flows westward through the southern part, and the Green River which flows south from the northernmost part of the plateau. The Green is a tributary of the Colorado, the confluence being west of Moab, Utah in Canyonlands National Park.

Mexican portion

The Mexican Plateau is one of six distinct physiographic sections of the Basin and Range Province, which in turn is part of the Intermontane Plateaus physiographic division. It is a large arid-to-semiarid plateau that occupies much of northern and central Mexico. Averaging 1,825 m (5,988 ft) above sea level, it extends from the United States border in the north to the Trans-Mexican Volcanic Belt in the south, and is bounded by the Sierra Madre Occidental and Sierra Madre Oriental to the west and east, respectively. 

A low east–west mountain range in the state of Zacatecas divides the plateau into northern and southern sections. These two sections, called the Northern Plateau (Spanish: Mesa del Norte) and Central Plateau (Spanish: Mesa Central), are now generally regarded by geographers as sections of one plateau.

The Little Ice Age – Back to the Future

April 4, 2019

What’s Natural

By Jim Steele
Original link: https://wattsupwiththat.com/2019/04/04/the-little-ice-age-back-to-the-future/?fbclid=IwAR20VdNKh0G3M3sr47CPnbTbdo8eaXhLOcqZifFgBmWpuJcQMmdUKppzxv0 

Extreme scientists and politicians warn we will suffer catastrophic climate change if the earth’s average temperature rises 2.7°F above the Little Ice Age average. They claim we are in a climate crisis because average temperature has already warmed by 1.5°F since 1850 AD. Guided by climate fear, politicians fund whacky engineering schemes to shade the earth with mirrors or aerosols to lower temperatures. But the cooler Little Ice Age endured a much more disastrous climate.

The Little Ice Age coincides with the pre-industrial period. The Little Ice Age spanned a period from 1300 AD to 1850 AD, but the exact timing varies. It was a time of great droughts, retreating tree lines, and agricultural failures leading to massive global famines and rampant epidemics. Meanwhile advancing glaciers demolished European villages and farms and extensive sea ice blocked harbors and prevented trade.

Dr. Michael Mann who preaches dire predictions wrought by global warming described the Little Ice Age as a period of widespread “famine, disease, and increased child mortality in Europe during the 17th–19th century, probably related, at least in part, to colder temperatures and altered weather conditions.” In contrast to current models suggesting global warming will cause wild weather swings, Mann concluded “the Little Ice Age may have been more significant in terms of increased variability of the climate”. Indeed, historical documents from the Little Ice Age describe wild climate swings with extremely cold winters followed by very warm summers, and cold wet years followed by cold dry years.

A series of Little Ice Age droughts lasting several decades devastated Asia between the mid 1300s and 1400s. Resulting famines caused significant societal upheaval within India, China, Sri Lanka, and Cambodia. Bad weather resulted in the Great Famine of 1315-1317 which decimated Europe causing extreme levels of crime, disease, mass death, cannibalism and infanticide. The North American tree-ring data reveal megadroughts lasting several decades during the cool 1500s. The Victorian Great Drought from 1876 to 1878 brought great suffering across much of the tropics with India devastated the most. More than 30 million people are thought to have died at this time from famine worldwide.

The Little Ice Age droughts and famines forced great societal upheaval, and the resulting climate change refugees were forced to seek better lands. But those movements also spread horrendous epidemics. Wild climate swings brought cold and dry weather to central Asia. That forced the Mongols to search for better grazing. As they invaded new territories they spread the Bubonic plague which had devastated parts of Asia earlier. In the 1300s the Mongols passed the plague to Italian merchant ships who then brought it to Europe where it quickly killed one third of Europe’s population. European explorers looking for new trade routes brought smallpox to the Americas, causing small native tribes to go extinct and decimating 25% to 50% of larger tribes. Introduced diseases rapidly reduced Mexico’s population from 30 million to 3 million.

By the 1700s a new killer began to dominate – accidental hypothermia. When indoor temperatures fall below 48°F for prolonged periods, the human body struggles to keep warm, setting off a series of reactions that causes stress and can result in heart attacks. As recently as the 1960s in Great Britain, 20,000 elderly and malnourished people who lacked central heating died from accidental hypothermia. As people with poor heating faced bouts of extreme cold in the 1700s, accidental hypothermia was rampant.

What caused the tragic climate changes of the Little Ice Age? Some scientists suggest lower solar output associated with periods of fewer sunspots. Increasing solar output then reversed the cooling and warmed the 20^th century world. As solar output is now falling to the lows of the Little Ice Age, a natural experiment is now in progress testing that solar theory. However other scientists suggest it was rising CO₂ that delivered the world from the Little Ice Age.

Increasing CO₂ also has a beneficial fertilization effect that is greening the earth. The 20^th century warming, whether natural or driven by rising CO₂ concentrations, has lengthened the growing season. Famines are being eliminated. Tree-lines stopped retreating and trees are now reclaiming territory lost over the past 500 years. So why is it that now we face a climate crisis?

At the end of the 1300’s Great Famine and the Bubonic Plague epidemic, the earth sustained 350 million people. With today’s advances in technology and milder growing conditions, record high crop yields are now feeding a human population that ballooned to over 7.6 billion.

So, the notion that cooler times represent the “good old days” and we are now in a warmer climate crisis seems truly absurd.

Jim Steele is retired director of the Sierra Nevada Field Campus, SFSU

and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism

Extinction debt

From Wikipedia, the free encyclopedia

In ecology, extinction debt is the future extinction of species due to events in the past. The phrases dead clade walking and survival without recovery express the same idea. 

Extinction debt occurs because of time delays between impacts on a species, such as destruction of habitat, and the species' ultimate disappearance. For instance, long-lived trees may survive for many years even after reproduction of new trees has become impossible, and thus they may be committed to extinction. Technically, extinction debt generally refers to the number of species in an area likely to become extinct, rather than the prospects of any one species, but colloquially it refers to any occurrence of delayed extinction.

Extinction debt may be local or global, but most examples are local as these are easier to observe and model. It is most likely to be found in long-lived species and species with very specific habitat requirements (specialists). Extinction debt has important implications for conservation, as it implies that species may become extinct due to past habitat destruction, even if continued impacts cease, and that current reserves may not be sufficient to maintain the species that occupy them. Interventions such as habitat restoration may reverse extinction debt.

Immigration credit is the corollary to extinction debt. It refers to the number of species likely to immigrate to an area after an event such as the restoration of an ecosystem.

Terminology

The term extinction debt was first used in 1994 in a paper by David Tilman, Robert May, Clarence Lehman and Martin Nowak, although Jared Diamond used the term "relaxation time" to describe a similar phenomenon in 1972.

Extinction debt is also known by the terms dead clade walking and survival without recovery when referring to the species affected. The phrase "dead clade walking" was coined by David Jablonski as early as 2001 as a reference to Dead Man Walking, a film whose title is based on American prison slang for a condemned prisoner's last walk to the execution chamber. "Dead clade walking" has since appeared in other scientists' writings about the aftermaths of mass extinctions.

In discussions of threats to biodiversity, extinction debt is analogous to the "climate commitment" in climate change, which states that inertia will cause the earth to continue to warm for centuries even if no more greenhouse gasses are emitted. Similarly, the current extinction may continue long after human impacts on species halt.

Causes

Jablonski recognized at least four patterns in the fossil record following mass extinctions:

(1) survival without recovery

also called “dead clade walking” – a group dwindling to extinction or relegation to precarious, minor ecological niches

(2) continuity with setbacks

patterns disturbed by the extinction event but soon continuing on the previous trajectory

(3) unbroken continuity

large-scale patterns continuing with little disruption

(4) unbridled diversification

an increase in diversity and species richness, as in the mammals following the end-Cretaceous extinction event

Extinction debt is caused by many of the same drivers as extinction. The most well-known drivers of extinction debt are habitat fragmentation and habitat destruction. These cause extinction debt by reducing the ability of species to persist via immigration to new habitats. Under equilibrium conditions, species may become extinct in one habitat patch, yet continues to survive because it can disperse to other patches. However, as other patches have been destroyed or rendered inaccessible due to fragmentation, this "insurance" effect is reduced and the species may ultimately become extinct. 

Pollution may also cause extinction debt by reducing a species' birth rate or increasing its death rate so that its population slowly declines. Extinction debts may be caused by invasive species or by climate change. 

Extinction debt may also occur due to the loss of mutualist species. In New Zealand, the local extinction of several species of pollinating birds in 1870 has caused a long-term reduction in the reproduction of the shrub species Rhabdothamnus solandri, which requires these birds to produce seeds. However, as the plant is slow-growing and long-lived, its populations persist.

Jablonski found that the extinction rate of marine invertebrates was significantly higher in the stage (major subdivision of an epoch – typically 2–10 million years' duration) following a mass extinction than in the stages preceding the mass extinction. His analysis focused on marine molluscs since they constitute the most abundant group of fossils and are therefore the least likely to produce sampling errors. Jablonski suggested that two possible explanations deserved further study:

• Post-extinction physical environments differed from pre-extinction environments in ways which were disadvantageous to the "dead clades walking".
• Ecosystems that developed after recoveries from mass extinctions may have been less favorable for the "dead clades walking".

Time scale

The time to "payoff" of extinction debt can be very long. Islands that lost habitat at the end of the last ice age 10,000 years ago still appear to be losing species as a result. It has been shown that some bryozoans, a type of microscopic marine organism, became extinct due to the volcanic rise of the Isthmus of Panama. This event cut off the flow of nutrients from the Pacific Ocean to the Caribbean 3–4.5 million years ago. While bryozoan populations dropped severely at this time, extinction of these species took another 1–2 million years.

Extinction debts incurred due to human actions have shorter timescales. Local extinction of birds from rainforest fragmentation occurs over years or decades, while plants in fragmented grasslands show debts lasting 50–100 years. Tree species in fragmented temperate forests have debts lasting 200 years or more.

Theoretical development

Origins in metapopulation models

Tilman et al. demonstrated that extinction debt could occur using a mathematical ecosystem model of species metapopulations. Metapopulations are multiple populations of a species that live in separate habitat patches or islands but interact via immigration between the patches. In this model, species persist via a balance between random local extinctions in patches and colonization of new patches. Tilman et al. used this model to predict that species would persist long after they no longer had sufficient habitat to support them. When used to estimate extinction debts of tropical tree species, the model predicted debts lasting 50–400 years.

One of the assumptions underlying the original extinction debt model was a trade-off between species' competitive ability and colonization ability. That is, a species that competes well against other species, and is more likely to become dominant in an area, is less likely to colonize new habitats due to evolutionary trade-offs. One of the implications of this assumption is that better competitors, which may even be more common than other species, are more likely to become extinct than rarer, less competitive, better dispersing species. This has been one of the more controversial components of the model, as there is little evidence for this trade-off in many ecosystems, and in many empirical studies dominant competitors were least likely species to become extinct. A later modification of the model showed that these trade-off assumptions may be relaxed, but need to exist partially, in order for the theory to work.

Development in other models

Further theoretical work has shown that extinction debt can occur under many different circumstances, driven by different mechanisms and under different model assumptions. The original model predicted extinction debt as a result of habitat destruction in a system of small, isolated habitats such as islands. Later models showed that extinction debt could occur in systems where habitat destruction occurs in small areas within a large area of habitat, as in slash-and-burn agriculture in forests, and could also occur due to decreased growth of species from pollutants. Predicted patterns of extinction debt differ between models, though. For instance, habitat destruction resembling slash-and-burn agriculture is thought to affect rare species rather than poor colonizers. Models that incorporate stochasticity, or random fluctuation in populations, show extinction debt occurring over different time scales than classic models.

Most recently, extinction debts have been estimated through the use models derived from neutral theory. Neutral theory has very different assumptions than the metapopulation models described above. It predicts that the abundance and distribution of species can be predicted entirely through random processes, without considering the traits of individual species. As extinction debt arises in models under such different assumptions, it is robust to different kinds of models. Models derived from neutral theory have successfully predicted extinction times for a number of bird species, but perform poorly at both very small and very large spatial scales.

Mathematical models have also shown that extinction debt will last longer if it occurs in response to large habitat impacts (as the system will move farther from equilibrium), and if species are long-lived. Also, species just below their extinction threshold, that is, just below the population level or habitat occupancy levels required sustain their population, will have long-term extinction debts. Finally, extinction debts are predicted to last longer in landscapes with a few large patches of habitat, rather than many small ones.

Detection

Extinction debt is difficult to detect and measure. Processes that drive extinction debt are inherently slow and highly variable (noisy), and it is difficult to locate or count the very small populations of near-extinct species. Because of these issues, most measures of extinction debt have a great deal of uncertainty.

Experimental evidence

Due to the logistical and ethical difficulties of inciting extinction debt, there are few studies of extinction debt in controlled experiments. However, experiments microcosms of insects living on moss habitats demonstrated that extinction debt occurs after habitat destruction. In these experiments, it took 6–12 months for species to die out following the destruction of habitat.

Observational methods

Long-term observation

Extinction debts that reach equilibrium in relatively short time scales (years to decades) can be observed via measuring the change in species numbers in the time following an impact on habitat. For instance, in the Amazon rainforest, researchers have measured the rate at which bird species disappear after forest is cut down. As even short-term extinction debts can take years to decades to reach equilibrium, though, such studies take many years and good data are rare.

Comparing the past and present

Most studies of extinction debt compare species numbers with habitat patterns from the past and habitat patterns in the present. If the present populations of species are more closely related to past habitat patterns than present, extinction debt is a likely explanation. The magnitude of extinction debt (i.e., number of species likely to become extinct) can not be estimated by this method.

If one has information on species populations from the past in addition to the present, the magnitude of extinction debt can be estimated. One can use the relationship between species and habitat from the past to predict the number of species expected in the present. The difference between this estimate and the actual number of species is the extinction debt.

This method requires the assumption that in the past species and their habitat were in equilibrium, which is often unknown. Also, a common relationship used to equate habitat and species number is the species-area curve, but as the species-area curve arises from very different mechanisms than those in metapopulation based models, extinction debts measured in this way may not conform with metapopulation models' predictions. The relationship between habitat and species number can also be represented by much more complex models that simulate the behavior of many species independently.

Comparing impacted and pristine habitats

If data on past species numbers or habitat are not available, species debt can also be estimated by comparing two different habitats: one which is mostly intact, and another which has had areas cleared and is smaller and more fragmented. One can then measure the relationship of species with the condition of habitat in the intact habitat, and, assuming this represents equilibrium, use it to predict the number of species in the cleared habitat. If this prediction is lower than the actual number of species in the cleared habitat, then the difference represents extinction debt. This method requires many of the same assumptions as methods comparing the past and present.

Examples

Grasslands

Studies of European grasslands show evidence of extinction debt through both comparisons with the past and between present-day systems with different levels of human impacts. The species diversity of grasslands in Sweden appears to be a remnant of more connected landscapes present 50 to 100 years ago. In alvar grasslands in Estonia that have lost area since the 1930s, 17–70% of species are estimated to be committed to extinction. However, studies of similar grasslands in Belgium, where similar impacts have occurred, show no evidence of extinction debt. This may be due to differences in the scale of measurement or the level of specialization of grass species.

Forests

Forests in Vlaams-Brabant, Belgium, show evidence of extinction debt remaining from deforestation that occurred between 1775 and 1900. Detailed modeling of species behavior, based on similar forests in England that did not experience deforestation, showed that long-lived and slow-growing species were more common than equilibrium models would predict, indicating that their presence was due to lingering extinction debt.

In Sweden, some species of lichens show an extinction debt in fragments of ancient forest. However, species of lichens that are habitat generalists, rather than specialists, do not.

Insects

Extinction debt has been found among species of butterflies living in the grasslands on Saaremaa and Muhu – islands off the western coast of Estonia. Butterfly species distributions on these islands are better explained by the habitat in the past than current habitats.

On the islands of the Azores Archipelago, more than 95% of native forests have been destroyed in the past 600 years. As a result, more than half of arthropods on these islands are believed to be committed to extinction, with many islands likely to lose more than 90% of species.

Vertebrates

80–90% of extinction from past deforestation in the Amazon has yet to occur, based on modeling based on species-area relationships. Local extinctions of approximately 6 species are expected in each 2500 km² region by 2050 due to past deforestation. Birds in the Amazon rain forest continued to become extinct locally for 12 years following logging that broke up contiguous forest into smaller fragments. The extinction rate slowed, however, as forest regrew in the spaces in between habitat fragments.

Countries in Africa are estimated to have, on average, a local extinction debt of 30% for forest-dwelling primates. That is, they are expected to have 30% of their forest primate species to become extinct in the future due to loss of forest habitat. The time scale for these extinctions has not been estimated.

Based on historical species-area relationships, Hungary currently has approximately nine more species of raptors than are thought to be able to be supported by current nature reserves.

Applications to conservation

The existence of extinction debt in many different ecosystems has important implications for conservation. It implies that in the absence of further habitat destruction or other environmental impacts, many species are still likely to become extinct. Protection of existing habitats may not be sufficient to protect species from extinction. However, the long time scales of extinction debt may allow for habitat restoration in order to prevent extinction, as occurred in the slowing of extinction in Amazon forest birds above. In another example, it has been found that grizzly bears in very small reserves in the Rocky Mountains are likely to become extinct, but this finding allows the modification of reserve networks to better support their populations.

The extinction debt concept may require revision of the value of land for species conservation, as the number of species currently present in a habitat may not be a good measure of the habitat's ability to support species in the future. As extinction debt may last longest near extinction thresholds, it may be hardest to detect the threat of extinction for species that conservation could benefit the most.

Economic analyses have shown that including extinction in management decision-making process changes decision outcomes, as the decision to destroy habitat changes conservation value in the future as well as the present. It is estimated that in Costa Rica, ongoing extinction debt may cost between $88 million and $467 million.

In popular culture

• An episode of the CBS series Elementary was named "Dead Clade Walking", and featured a Nanotyrannus skeleton found "significantly above" the K-T boundary.

Habitat destruction

From Wikipedia, the free encyclopedia

Habitat destruction is the process by which natural habitat becomes incapable of supporting its native species. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity is mainly for the purpose of harvesting natural resources for industrial production and urbanization. Clearing habitats for agriculture is the principal cause of habitat destruction. Other important causes of habitat destruction include mining, logging, trawling, and urban sprawl. Habitat destruction is currently ranked as the primary cause of species extinction worldwide. It is a process of natural environmental change that may be caused by habitat fragmentation, geological processes, climate change or by human activities such as the introduction of invasive species, ecosystem nutrient depletion, and other human activities.

 

The terms habitat loss and habitat reduction are also used in a wider sense, including loss of habitat from other factors, such as water and noise pollution.

Impacts on organisms

In the simplest term, when a habitat is destroyed, the plants, animals, and other organisms that occupied the habitat have a reduced carrying capacity so that populations decline and extinction becomes more likely. Perhaps the greatest threat to organisms and biodiversity is the process of habitat loss. Temple (1986) found that 82% of endangered bird species were significantly threatened by habitat loss. Most amphibian species are also threatened by habitat loss, and some species are now only breeding in modified habitat. Endemic organisms with limited ranges are most affected by habitat destruction, mainly because these organisms are not found anywhere else within the world, and thus have less chance of recovering. Many endemic organisms have very specific requirements for their survival that can only be found within a certain ecosystem, resulting in their extinction. Extinction may also take place very long after the destruction of habitat, a phenomenon known as extinction debt. Habitat destruction can also decrease the range of certain organism populations. This can result in the reduction of genetic diversity and perhaps the production of infertile youths, as these organisms would have a higher possibility of mating with related organisms within their population, or different species. One of the most famous examples is the impact upon China's giant panda, once found across the nation. Now it is only found in fragmented and isolated regions in the southwest of the country, as a result of widespread deforestation in the 20th century.

Geography

Satellite photograph of deforestation in Bolivia. Originally dry tropical forest, the land is being cleared for soybean cultivation.

 

Biodiversity hotspots are chiefly tropical regions that feature high concentrations of endemic species and, when all hotspots are combined, may contain over half of the world’s terrestrial species. These hotspots are suffering from habitat loss and destruction. Most of the natural habitat on islands and in areas of high human population density has already been destroyed (WRI, 2003). Islands suffering extreme habitat destruction include New Zealand, Madagascar, the Philippines, and Japan. South and East Asia — especially China, India, Malaysia, Indonesia, and Japan — and many areas in West Africa have extremely dense human populations that allow little room for natural habitat. Marine areas close to highly populated coastal cities also face degradation of their coral reefs or other marine habitat. These areas include the eastern coasts of Asia and Africa, northern coasts of South America, and the Caribbean Sea and its associated islands.

Regions of unsustainable agriculture or unstable governments, which may go hand-in-hand, typically experience high rates of habitat destruction. Central America, Sub-Saharan Africa, and the Amazonian tropical rainforest areas of South America are the main regions with unsustainable agricultural practices and/or government mismanagement.

Areas of high agricultural output tend to have the highest extent of habitat destruction. In the U.S., less than 25% of native vegetation remains in many parts of the East and Midwest. Only 15% of land area remains unmodified by human activities in all of Europe.

Ecosystems

Jungle burned for agriculture in southern Mexico

 

Tropical rainforests have received most of the attention concerning the destruction of habitat. From the approximately 16 million square kilometers of tropical rainforest habitat that originally existed worldwide, less than 9 million square kilometers remain today. The current rate of deforestation is 160,000 square kilometers per year, which equates to a loss of approximately 1% of original forest habitat each year.

Other forest ecosystems have suffered as much or more destruction as tropical rainforests. Farming and logging have severely disturbed at least 94% of temperate broadleaf forests; many old growth forest stands have lost more than 98% of their previous area because of human activities. Tropical deciduous dry forests are easier to clear and burn and are more suitable for agriculture and cattle ranching than tropical rainforests; consequently, less than 0.1% of dry forests in Central America's Pacific Coast and less than 8% in Madagascar remain from their original extents.

Farmers near newly cleared land within Taman Nasional Kerinci Seblat (Kerinci Seblat National Park), Sumatra.

 

Plains and desert areas have been degraded to a lesser extent. Only 10-20% of the world's drylands, which include temperate grasslands, savannas, and shrublands, scrub, and deciduous forests, have been somewhat degraded. But included in that 10-20% of land is the approximately 9 million square kilometers of seasonally dry-lands that humans have converted to deserts through the process of desertification. The tallgrass prairies of North America, on the other hand, have less than 3% of natural habitat remaining that has not been converted to farmland.

Wetlands and marine areas have endured high levels of habitat destruction. More than 50% of wetlands in the U.S. have been destroyed in just the last 200 years. Between 60% and 70% of European wetlands have been completely destroyed. In the United Kingdom, there has been an increase in demand for coastal housing and tourism which has caused a decline in marine habitats over the last 60 years. The rising sea levels and temperatures have caused soil erosion, coastal flooding, and loss of quality in the UK marine ecosystem. About one-fifth (20%) of marine coastal areas have been highly modified by humans. One-fifth of coral reefs have also been destroyed, and another fifth has been severely degraded by overfishing, pollution, and invasive species; 90% of the Philippines’ coral reefs alone have been destroyed. Finally, over 35% of the mangrove ecosystems worldwide have been destroyed.

Natural causes

Habitat destruction through natural processes such as volcanism, fire, and climate change is well documented in the fossil record. One study shows that habitat fragmentation of tropical rainforests in Euramerica 300 million years ago led to a great loss of amphibian diversity, but simultaneously the drier climate spurred on a burst of diversity among reptiles.

Human causes

Deforestation and roads in Amazonia, the Amazon Rainforest.

 

Habitat destruction caused by humans includes land conversion from forests, etc. to arable land, urban sprawl, infrastructure development, and other anthropogenic changes to the characteristics of land. Habitat degradation, fragmentation, and pollution are aspects of habitat destruction caused by humans that do not necessarily involve over destruction of habitat, yet result in habitat collapse. Desertification, deforestation, and coral reef degradation are specific types of habitat destruction for those areas (deserts, forests, coral reefs). 

Geist and Lambin (2002) assessed 152 case studies of net losses of tropical forest cover to determine any patterns in the proximate and underlying causes of tropical deforestation. Their results, yielded as percentages of the case studies in which each parameter was a significant factor, provide a quantitative prioritization of which proximate and underlying causes were the most significant. The proximate causes were clustered into broad categories of agricultural expansion (96%), infrastructure expansion (72%), and wood extraction (67%). Therefore, according to this study, forest conversion to agriculture is the main land use change responsible for tropical deforestation. The specific categories reveal further insight into the specific causes of tropical deforestation: transport extension (64%), commercial wood extraction (52%), permanent cultivation (48%), cattle ranching (46%), shifting (slash and burn) cultivation (41%), subsistence agriculture (40%), and fuel wood extraction for domestic use (28%). One result is that shifting cultivation is not the primary cause of deforestation in all world regions, while transport extension (including the construction of new roads) is the largest single proximate factor responsible for deforestation.

Global warming

Rising global temperatures, caused by the greenhouse effect, contribute to habitat destruction, endangering various species, such as the polar bear. Melting ice caps promote rising sea levels and floods which threaten natural habitats and species globally.

Drivers

Nanjing Road in Shanghai

 

While the above-mentioned activities are the proximal or direct causes of habitat destruction in that they actually destroy habitat, this still does not identify why humans destroy habitat. The forces that cause humans to destroy habitat are known as drivers of habitat destruction. Demographic, economic, sociopolitical, scientific and technological, and cultural drivers all contribute to habitat destruction.

Demographic drivers include the expanding human population; rate of population increase over time; spatial distribution of people in a given area (urban versus rural), ecosystem type, and country; and the combined effects of poverty, age, family planning, gender, and education status of people in certain areas. Most of the exponential human population growth worldwide is occurring in or close to biodiversity hotspots. This may explain why human population density accounts for 87.9% of the variation in numbers of threatened species across 114 countries, providing indisputable evidence that people play the largest role in decreasing biodiversity. The boom in human population and migration of people into such species-rich regions are making conservation efforts not only more urgent but also more likely to conflict with local human interests. The high local population density in such areas is directly correlated to the poverty status of the local people, most of whom lacking an education and family planning.

From the Geist and Lambin (2002) study described in the previous section, the underlying driving forces were prioritized as follows (with the percent of the 152 cases the factor played a significant role in): economic factors (81%), institutional or policy factors (78%), technological factors (70%), cultural or socio-political factors (66%), and demographic factors (61%). The main economic factors included commercialization and growth of timber markets (68%), which are driven by national and international demands; urban industrial growth (38%); low domestic costs for land, labor, fuel, and timber (32%); and increases in product prices mainly for cash crops (25%). Institutional and policy factors included formal pro-deforestation policies on land development (40%), economic growth including colonization and infrastructure improvement (34%), and subsidies for land-based activities (26%); property rights and land-tenure insecurity (44%); and policy failures such as corruption, lawlessness, or mismanagement (42%). The main technological factor was the poor application of technology in the wood industry (45%), which leads to wasteful logging practices. Within the broad category of cultural and sociopolitical factors are public attitudes and values (63%), individual/household behavior (53%), public unconcern toward forest environments (43%), missing basic values (36%), and unconcern by individuals (32%). Demographic factors were the in-migration of colonizing settlers into sparsely populated forest areas (38%) and growing population density—a result of the first factor—in those areas (25%). 

There are also feedbacks and interactions among the proximate and underlying causes of deforestation that can amplify the process. Road construction has the largest feedback effect, because it interacts with—and leads to—the establishment of new settlements and more people, which causes a growth in wood (logging) and food markets. Growth in these markets, in turn, progresses the commercialization of agriculture and logging industries. When these industries become commercialized, they must become more efficient by utilizing larger or more modern machinery that often has a worse effect on the habitat than traditional farming and logging methods. Either way, more land is cleared more rapidly for commercial markets. This common feedback example manifests just how closely related the proximate and underlying causes are to each other.

Impact on human population

The draining and development of coastal wetlands that previously protected the Gulf Coast contributed to severe flooding in New Orleans, Louisiana in the aftermath of Hurricane Katrina.

 

Habitat destruction vastly increases an area's vulnerability to natural disasters like flood and drought, crop failure, spread of disease, and water contamination. On the other hand, a healthy ecosystem with good management practices will reduce the chance of these events happening, or will at least mitigate adverse impacts. 

Agricultural land can actually suffer from the destruction of the surrounding landscape. Over the past 50 years, the destruction of habitat surrounding agricultural land has degraded approximately 40% of agricultural land worldwide via erosion, salinization, compaction, nutrient depletion, pollution, and urbanization. Humans also lose direct uses of natural habitat when habitat is destroyed. Aesthetic uses such as birdwatching, recreational uses like hunting and fishing, and ecotourism usually rely upon virtually undisturbed habitat. Many people value the complexity of the natural world and are disturbed by the loss of natural habitats and animal or plant species worldwide.

Probably the most profound impact that habitat destruction has on people is the loss of many valuable ecosystem services. Habitat destruction has altered nitrogen, phosphorus, sulfur, and carbon cycles, which has increased the frequency and severity of acid rain, algal blooms, and fish kills in rivers and oceans and contributed tremendously to global climate change. One ecosystem service whose significance is becoming better understood is climate regulation. On a local scale, trees provide windbreaks and shade; on a regional scale, plant transpiration recycles rainwater and maintains constant annual rainfall; on a global scale, plants (especially trees from tropical rainforests) from around the world counter the accumulation of greenhouse gases in the atmosphere by sequestering carbon dioxide through photosynthesis. Other ecosystem services that are diminished or lost altogether as a result of habitat destruction include watershed management, nitrogen fixation, oxygen production, pollination (see pollinator decline), waste treatment (i.e., the breaking down and immobilization of toxic pollutants), and nutrient recycling of sewage or agricultural runoff.

The loss of trees from the tropical rainforests alone represents a substantial diminishing of the earth’s ability to produce oxygen and use up carbon dioxide. These services are becoming even more important as increasing carbon dioxide levels is one of the main contributors to global climate change. 

The loss of biodiversity may not directly affect humans, but the indirect effects of losing many species as well as the diversity of ecosystems in general are enormous. When biodiversity is lost, the environment loses many species that perform valuable and unique roles in the ecosystem. The environment and all its inhabitants rely on biodiversity to recover from extreme environmental conditions. When too much biodiversity is lost, a catastrophic event such as an earthquake, flood, or volcanic eruption could cause an ecosystem to crash, and humans would obviously suffer from that. Loss of biodiversity also means that humans are losing animals that could have served as biological control agents and plants that could potentially provide higher-yielding crop varieties, pharmaceutical drugs to cure existing or future diseases or cancer, and new resistant crop varieties for agricultural species susceptible to pesticide-resistant insects or virulent strains of fungi, viruses, and bacteria.

The negative effects of habitat destruction usually impact rural populations more directly than urban populations. Across the globe, poor people suffer the most when natural habitat is destroyed, because less natural habitat means fewer natural resources per capita, yet wealthier people and countries simply have to pay more to continue to receive more than their per capita share of natural resources.

Another way to view the negative effects of habitat destruction is to look at the opportunity cost of destroying a given habitat. In other words, what are people losing out on by taking away a given habitat? A country may increase its food supply by converting forest land to row-crop agriculture, but the value of the same land may be much larger when it can supply natural resources or services such as clean water, timber, ecotourism, or flood regulation and drought control.

Outlook

The rapid expansion of the global human population is increasing the world’s food requirement substantially. Simple logic dictates that more people will require more food. In fact, as the world’s population increases dramatically, agricultural output will need to increase by at least 50%, over the next 30 years. In the past, continually moving to new land and soils provided a boost in food production to meet the global food demand. That easy fix will no longer be available, however, as more than 98% of all land suitable for agriculture is already in use or degraded beyond repair.

The impending global food crisis will be a major source of habitat destruction. Commercial farmers are going to become desperate to produce more food from the same amount of land, so they will use more fertilizers and show less concern for the environment to meet the market demand. Others will seek out new land or will convert other land-uses to agriculture. Agricultural intensification will become widespread at the cost of the environment and its inhabitants. Species will be pushed out of their habitat either directly by habitat destruction or indirectly by fragmentation, degradation, or pollution. Any efforts to protect the world’s remaining natural habitat and biodiversity will compete directly with humans’ growing demand for natural resources, especially new agricultural lands.

Solutions

Chelonia mydas on a Hawaiian coral reef. Although the endangered species is protected, habitat loss from human development is a major reason for the loss of green turtle nesting beaches.

 

In most cases of tropical deforestation, three to four underlying causes are driving two to three proximate causes. This means that a universal policy for controlling tropical deforestation would not be able to address the unique combination of proximate and underlying causes of deforestation in each country. Before any local, national, or international deforestation policies are written and enforced, governmental leaders must acquire a detailed understanding of the complex combination of proximate causes and underlying driving forces of deforestation in a given area or country. This concept, along with many other results of tropical deforestation from the Geist and Lambin study, can easily be applied to habitat destruction in general. Governmental leaders need to take action by addressing the underlying driving forces, rather than merely regulating the proximate causes. In a broader sense, governmental bodies at a local, national, and international scale need to emphasize the following:

1. Considering the many irreplaceable ecosystem services provided by natural habitats.
2. Protecting remaining intact sections of natural habitat.
3. Educating the public about the importance of natural habitat and biodiversity.
4. Developing family planning programs in areas of rapid population growth.
5. Finding ecological ways to increase agricultural output without increasing the total land in production.
6. Preserving habitat corridors to minimize prior damage from fragmented habitats.
7. Reducing human population and expansion. Apart from improving access to contraception globally, furthering gender equality also has a great benefit. When women have the same education (decision-making power), this generally leads to smaller families.

An Oxford researcher says there are seven moral rules that unite humanity

By Jenny AndersonMarch 6, 2019

Original link:  https://qz.com/1562585/the-seven-moral-rules-that-supposedly-unite-humanity/?fbclid=IwAR0uBvcefirpHecuDBPjQdQjwZQqWLrEtXe2DIPVwkTsDIrVdzMFZPNIWTg

In 2012, Oliver Scott Curry was an anthropology lecturer at the University of Oxford. One day, he organized a debate among his students about whether morality was innate or acquired. One side argued passionately that morality was the same everywhere; the other, that morals were different everywhere.

“I realized that, obviously, no one really knew, and so decided to find out for myself,” Curry says.

Seven years later, Curry, now a senior researcher at Oxford’s Institute for Cognitive and Evolutionary Anthropology, can offer up an answer to the seemingly ginormous question of what morality is and how it does—or doesn’t—vary around the world.

Morality, he says, is meant to promote cooperation. “People everywhere face a similar set of social problems, and use a similar set of moral rules to solve them,” he says as lead author of a paper recently published in Current Anthropology. “Everyone everywhere shares a common moral code. All agree that cooperating, promoting the common good, is the right thing to do.”

For the study, Curry’s group studied ethnographic accounts of ethics from 60 societies, across over 600 sources. The universal rules of morality are:

1. Help your family
2. Help your group
3. Return favors
4. Be brave
5. Defer to superiors
6. Divide resources fairly
7. Respect others’ property

The authors reviewed seven “well-established” types of cooperation to test the idea that morality evolved to promote cooperation, including family values, or why we allocate resources to family; group loyalty, or why we form groups, conform to local norms, and promote unity and solidarity; social exchange or reciprocity, or why we trust others, return favors, seek revenge, express gratitude, feel guilt, and make up after fights; resolving conflicts through contests which entail “hawkish displays of dominance” such as bravery or “dovish displays of submission,” such as humility or deference; fairness, or how to divide disputed resources equally or compromise; and property rights, that is, not stealing.

The team found that these seven cooperative behaviors were considered morally good in 99.9% of cases across cultures. Curry is careful to note that people around the world differ hugely in how they prioritize different cooperative behaviors. But he said the evidence was overwhelming in widespread adherence to those moral values.

“I was surprised by how unsurprising it all was,” he says. “I expected there would be lots of ‘be brave,’  ‘don’t steal from others,’ and ‘return favors,’ but I also expected a lot of strange, bizarre moral rules.” They did find the occasional departure from the norm. For example, among the Chuukese, the largest ethnic group in the Federated States of Micronesia, “to steal openly from others is admirable in that it shows a person’s dominance and demonstrates that he is not intimidated by the aggressive powers of others.” That said, researchers who studied the group concluded that the seven universal moral rules still apply to this behavior: “it appears to be a case in which one form of cooperation (respect for property) has been trumped by another (respect for a hawkish trait, although not explicitly bravery),” they wrote.

Plenty of studies have looked at some rules of morality in some places, but none have attempted to examined the rules of morality in such a large sample of societies. Indeed, when Curry was trying to get funding, his idea was repeatedly rejected as either too obvious or too impossible to prove.

The question of whether morality is universal or relative is an age-old one. In the 17th century, John Locke wrote that if you look around the world, “you could be sure that there is scarce that principle of morality to be named, or rule of virtue to be thought on …. which is not, somewhere or other, slighted and condemned by the general fashion of whole societies of men.”

Philosopher David Hume disagreed. He wrote that moral judgments depend on an “internal sense or feeling, which nature has made universal in the whole species,” noting that certain qualities, including “truth, justice, courage, temperance, constancy, dignity of mind . . . friendship, sympathy, mutual attachment, and fidelity” were pretty universal.

In a critique of Curry’s paper, Paul Bloom, a professor of psychology and cognitive science at Yale University, says that we are far from consensus on a definition of morality. Is it about fairness and justice, or about “maximizing the welfare of sentient beings?” Is it about delaying gratification for long-term gain, otherwise known as intertemporal choice—or maybe altruism?

Bloom also says that the authors of the Current Anthropology study do not sufficiently explain the way we come to moral judgements—that is, the roles that reason, emotions, brain structures, social forces, and development may play in shaping our ideas of morality. While the paper claims that moral judgments are universal because of “collection of instincts, intuitions, inventions, and institutions,” Bloom writes, the authors make “no specific claims about what’s innate, what’s learned, and what arises from personal choice.”

So perhaps the seven universal rules may not be the ultimate list. But at a time when it often feels like we don’t have much in common, Curry offers a framework to consider how we might.

“Humans are a very tribal species,” Curry says. “We are quick to divide into us and them.”