The environmental impact of agriculture is the effect that
different farming practices have on the ecosystems around them, and how
those effects can be traced back to those practices. The environmental
impact of agriculture varies based on the wide variety of agricultural practices employed around the world. Ultimately, the environmental impact
depends on the production practices of the system used by farmers. The
connection between emissions into the environment and the farming system
is indirect, as it also depends on other climate variables such as rainfall and temperature.
There are two types of indicators of environmental impact:
"means-based", which is based on the farmer's production methods, and
"effect-based", which is the impact that farming methods have on the
farming system or on emissions to the environment. An example of a
means-based indicator would be the quality of groundwater, that is
effected by the amount of nitrogen applied to the soil. An indicator
reflecting the loss of nitrate to groundwater would be effect-based.
The means-based evaluation looks at farmers' practices of agriculture,
and the effect-based evaluation considers the actual effects of the
agricultural system. For example, means-based analysis might look at
pesticides and fertilization methods that farmers are using, and
effect-based analysis would consider how much CO2 is being emitted or
what the Nitrogen content of the soil is.
The environmental impact of agriculture involves a variety of factors from the soil,
to water, the air, animal and soil variety, people, plants, and the
food itself. Some of the environmental issues that are related to
agriculture are climate change, deforestation, genetic engineering, irrigation problems, pollutants, soil degradation, and waste.
Negatives
Climate change
Climate change and agriculture are interrelated processes, both of which take place on a worldwide scale. Global warming is projected to have significant impacts on conditions affecting agriculture, including temperature, precipitation and glacial run-off. These conditions determine the carrying capacity of the biosphere to produce enough food for the human population and domesticated animals. Rising carbon dioxide
levels would also have effects, both detrimental and beneficial, on
crop yields. Assessment of the effects of global climate changes on
agriculture might help to properly anticipate and adapt farming to
maximize agricultural production.
Although the net impact of climate change on agricultural production is
uncertain it is likely that it will shift the suitable growing zones
for individual crops. Adjustment to this geographical shift will involve
considerable economic costs and social impacts.
At the same time, agriculture has been shown to produce
significant effects on climate change, primarily through the production
and release of greenhouse gases such as carbon dioxide, methane, and nitrous oxide. In addition, agriculture that practices tillage, fertilization, and pesticide application also releases ammonia, nitrate, phosphorus, and many other pesticides that affect air, water, and soil quality, as well as biodiversity. Agriculture also alters the Earth's land cover, which can change its ability to absorb or reflect heat and light, thus contributing to radiative forcing. Land use change such as deforestation and desertification, together with use of fossil fuels, are the major anthropogenic
sources of carbon dioxide; agriculture itself is the major contributor
to increasing methane and nitrous oxide concentrations in earth's atmosphere.
Deforestation
Deforestation is clearing the Earth's forests on a large scale
worldwide and resulting in many land damages. One of the causes of
deforestation is to clear land for pasture or crops. According to
British environmentalist Norman Myers, 5% of deforestation is due to cattle ranching, 19% due to over-heavy logging, 22% due to the growing sector of palm oil plantations, and 54% due to slash-and-burn farming.
Deforestation causes the loss of habitat for millions of species,
and is also a driver of climate change. Trees act as a carbon sink:
that is, they absorb carbon dioxide, an unwanted greenhouse gas, out of
the atmosphere. Removing trees releases carbon dioxide into the
atmosphere and leaves behind fewer trees to absorb the increasing amount
of carbon dioxide in the air. In this way, deforestation exacerbates
climate change. When trees are removed from forests, the soils tend to
dry out because there is no longer shade, and there are not enough trees
to assist in the water cycle
by returning water vapor back to the environment. With no trees,
landscapes that were once forests can potentially become barren deserts.
The removal of trees also causes extreme fluctuations in temperature.
In 2000 the United Nations Food and Agriculture Organization
(FAO) found that "the role of population dynamics in a local setting
may vary from decisive to negligible," and that deforestation can result
from "a combination of population pressure and stagnating economic,
social and technological conditions."
Irrigation
Irrigation can lead to a number of problems:
Among some of these problems is the depletion of underground aquifers through overdrafting. Soil can be over-irrigated because of poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution. Over-irrigation can cause deep drainage from rising water tables that can lead to problems of irrigation salinity requiring watertable control by some form of subsurface land drainage. However, if the soil is under irrigated, it gives poor soil salinity control which leads to increased soil salinity with consequent buildup of toxic salts on soil surface in areas with high evaporation. This requires either leaching to remove these salts and a method of drainage to carry the salts away. Irrigation with saline or high-sodium water may damage soil structure owing to the formation of alkaline soil.
Pollutants
Synthetic pesticides such as 'Malathion', 'Rogor', 'Kelthane' and 'confidor' are the most widespread method of controlling pests in agriculture. Pesticides can leach through the soil and enter the groundwater, as well as linger in food products and result in death in humans and non-targeted wildlife [DJS -- there is no evidence of this to any significant degree].
A wide range of agricultural chemicals are used and some become pollutants
through use, misuse, or ignorance. The erosion of topsoil, which can
contain chemicals such as herbicides and pesticides, can be carried away
from farms to other places. Pesticides can be found in streams and ground water. Atrazine is a herbicide used to control weeds that grow among crops.
This herbicide can disrupt endocrine production which can cause
reproductive problems in mammals, amphibians and fish that have been
exposed.
Pollutants from agriculture have a huge effect on water quality. Agricultural nonpoint source (NPS) solution impacts lakes, rivers, wetlands, estuaries, and groundwater.
Agricultural NPS can be caused by poorly managed animal feeding
operations, overgrazing, plowing, fertilizer, and improper, excessive,
or badly timed use of Pesticides. Pollutants from farming include sediments, nutrients, pathogens, pesticides, metals, and salts.
Animal agriculture can also cause pollutants to enter the environment.
Bacteria and pathogens in manure can make their way into streams and
groundwater if grazing, storing manure in lagoons and applying manure to
fields is not properly managed.
Listed below are additional and specific problems that may arise with the release of pollutants from agriculture.
- Pesticide drift
- soil contamination
- air pollution spray drift
- Pesticides, especially those based on organochloride
- Pesticide residue in foods
- Pesticide toxicity to bees
- Bioremediation
Soil degradation
Soil degradation
is the decline in soil quality that can be a result of many factors,
especially from agriculture. Soils hold the majority of the world's
biodiversity, and healthy soils are essential for food production and an
adequate water supply.
Common attributes of soil degradation can be salting, waterlogging,
compaction, pesticide contamination, decline in soil structure quality,
loss of fertility, changes in soil acidity, alkalinity, salinity, and erosion. Soil erosion is the wearing away of topsoil by water, wind, or farming activities. Topsoil is very fertile, which makes it valuable to farmers growing crops.
Soil degradation also has a huge impact on biological degradation,
which affects the microbial community of the soil and can alter nutrient
cycling, pest and disease control, and chemical transformation
properties of the soil.
Waste
Plasticulture is the use of plastic mulch
in agriculture. Farmers use plastic sheets as mulch to cover 50-70% of
the soil and allows them to use drip irrigation systems to have better
control over soil nutrients and moisture.
Rain is not required in this system, and farms that use plasticulture
are built to encourage the fastest runoff of rain. The use of pesticides with plasticulture allows pesticides to be transported easier in the surface runoff
towards wetlands or tidal creeks. The runoff from pesticides and
chemicals in the plastic can cause serious deformations and death in
shellfish as the runoff carries the chemicals towards the oceans.
In addition to the increased runoff that results from
plasticulture, there is also the problem of the increased amount of
waste form the plastic mulch itself. The use of plastic mulch for
vegetables, strawberries, and other row and orchard crops exceeds 110
million pounds annually in the United States. Most plastic ends up in
the landfill, although there are other disposal options such as disking
mulches into the soil, on-site burying, on-site storage, reuse,
recycling, and incineration. The incineration and recycling options are
complicated by the variety of the types of plastics that are used and by
the geographic dispersal of the plastics. Plastics also contain
stabilizers and dyes as well as heavy metals, which limits the amount of
products that can be recycled. Research is continually being conducted
on creating biodegradable or photodegradable
mulches. While there has been minor success with this, there is also
the problem of how long the plastic takes to degrade, as many
biodegradable products take a long time to break down.
Issues by region
The
environmental impact of agriculture can vary depending on the region as
well as the type of agriculture production method that is being used.
Listed below are some specific environmental issues in a various
different regions around the world.
- Hedgerow removal in the United Kingdom.
- Soil salinisation, especially in Australia.
- Phosphate mining in Nauru
- Methane emissions from livestock in New Zealand. See Climate change in New Zealand.
- Environmentalists attribute the hypoxic zone in the Gulf of Mexico as being encouraged by nitrogen fertilization of the algae bloom.
Sustainable agriculture
Sustainable agriculture
is the idea that agriculture should occur in a way such that we can
continue to produce what is necessary without infringing on the ability
for future generations to do the same.
The exponential population increase in recent decades has increased the practice of agricultural land conversion
to meet demand for food which in turn has increased the effects on the
environment. The global population is still increasing and will
eventually stabilise, as some critics doubt that food production, due to
lower yields from global warming, can support the global population.
Agriculture can have negative effects on biodiversity as well. Organic farming is a multifaceted sustainable agriculture
set of practices that can have a lower impact on the environment at the
small scale. However, in most cases organic farming results in lower
yields in terms of production per unit area.
Therefore, widespread adoption of organic agriculture will require
additional land to be cleared and water resources extracted to meet the
same level of production. A European meta-analysis found that organic
farms tended to have higher soil organic matter
content and lower nutrient losses (nitrogen leaching, nitrous oxide
emissions and ammonia emissions) per unit of field area but higher
ammonia emissions, nitrogen leaching and nitrous oxide emissions per
product unit. It is believed by many that conventional farming systems cause less rich biodiversity than organic systems. Organic farming
has shown to have on average 30% higher species richness than
conventional farming. Organic systems on average also have 50% more
organisms. This data has some issues because there were several results
that showed a negative effect on these things when in an organic farming
system.
The opposition to organic agriculture believes that these negatives are
an issue with the organic farming system. What began as a small scale,
environmentally conscious has now become just as industrialized as
conventional agriculture. This industrialization can lead to the issues
shown above such as climate change, and deforestation.
Conservation tillage
Conservation
tillage is an alternative tillage method for farming which is more
sustainable for the soil and surrounding ecosystem.
This is done by allowing the residue of the previous harvest's crops to
remain in the soil before tilling for the next crop. Conservation
tillage has shown to improve many things such as soil moisture
retention, and reduce erosion. Some disadvantages are the fact that more
expensive equipment is needed for this process, more pesticides will
need to be used, and the positive effects take a long time to be
visible.
The barriers of instantiating a conservation tillage policy are that
farmers are reluctant to change their methods, and would protest a more
expensive, and time consuming method of tillage than the conventional
one they are used to.