(par 5.4.3.2 ) Environmental impacts of farming

Environmental impacts of farming

http://wwf.panda.org/what_we_do/footprint/agriculture/impacts/

Unsustainable agricultural and aquaculture practices present the greatest immediate threat to species and ecosystems around the world.

Corn (Zea mays) growing in southern Ontario, Canada. © Frank Parhizgar / WWF-Canada

Farmed areas – both on land and in the water – provide important habitats for many wild plants and animals.

When farming operations are sustainably managed, they can help preserve and restore critical habitats, protect watersheds, and improve soil health and water quality.

But when practiced without care, farming presents the greatest threat to species and ecosystems.

Indeed, many of WWF’s priority places and species are negatively impacted by agriculture and/or aquaculture.

Multiple impacts

Negative environmental impacts from unsustainable farming practices include:

Land conversion & habitat loss
Wasteful water consumption
Soil erosion and degradation
Pollution
Climate change
Genetic erosion

Farming: Habitat conversion & loss

The main impact from farming comes from clearing natural habitats for agriculture and aquaculture – especially for intensive monocultures.

Wheat stacked up to dry in paddocks, Western Australia. In some parts of the Southwest Australia Ecoregion, more than 90% of the original native vegetation has been cleared to make way for agriculture. © Richard McLellan / WWF

A major – and growing – land use

Agriculture is a major land use. Around 50% of the world’s habitable land has already been converted to farming land. Overall, farmland covers 38% of the world’s land area.¹

This area is still expanding. It is predicted that in developing countries, a further 120 million hectares of natural habitats will be converted to farmland to meet demand for food by 2050. This will include land with high biodiversity value.

Natural habitats converted to monocultures

Agricultural ecosystems provide important habitats for many wild plant and animal species. This is especially the case for traditional farming areas that cultivate diverse species.

However, rising demand for food and other agricultural products has seen large-scale clearing of natural habitats to make room for intensive monocultures.

Recent examples include the conversion of lowland rainforests in Indonesia to oil palm plantations, and of large areas of the Amazon rainforest and Brazilian savanna to soybean and cattle farms.

This ongoing habitat loss threatens entire ecosystems as well as many species. Expanding oil palm plantations in Indonesia and Malaysia, for example, pose the most significant threats to endangered megafauna including Asian elephant, Sumatran rhinoceros, and tigers.

Freshwater and marine areas also affected

Aquaculture is also in direct competition with natural marine and freshwater habitats for space.

For example, marine fish farms often need the shelter of bays and estuaries to avoid damage from storms and currents. In addition, farmed fish need good water quality, frequent water exchange, and other optimal environmental conditions.

But these locations are also very often ideal for wild fish and other marine life.

Some European fish farms have been placed in the migratory routes of wild salmon, while in Asia and Latin America, mangrove forests have been cleared to make space for shrimp farms.

Land lost to desertification

On top of habitat loss due to clearing, unsustainable agricultural practices are seeing 12 million hectares of land lost each year to desertification.

Wasteful water consumption

Excessive water use for agriculture is leaving rivers, lakes and underground water sources dry in many irrigated areas.

Intensive cultivation of soybeans using rotary irrigation system, Goias State, Brazil. © Edward Parker / WWF

Agriculture: the greatest user of water

Globally, the agricultural sector consumes about 70% of the planet’s accessible freshwater¹ – more than twice that of industry (23%), and dwarfing municipal use (8%).

Wasteful and unsustainable

Many big food producing countries like the US, China, India, Pakistan, Australia and Spain have reached, or are close to reaching, their renewable water resource limits.

The main causes of wasteful and unsustainable water use are:

leaky irrigation systems
wasteful field application methods
cultivation of thirsty crops not suited to the environment.

The problem is made worse by misdirected subsidies, low public and political awareness of the crisis, and weak environmental legislation.

Multiple environmental impacts

Unsustainable water use harms the environment by changing the water table and/or depleting ground water supplies.

Excessive irrigation can also increase soil salinity and wash pollutants and sediment into rivers – causing damage to freshwater ecosystems and species as well as those further downstream, including coral reefs and coastal fish breeding grounds.

Soil erosion and degradation

Erosion commonly occurs following conversion of natural vegetation to agricultural land – carrying away fertile soil as well as fertilizers, pesticides and other agrochemicals.

Intensive agriculture is causing serious soil erosion in some areas of the Gulf of California, Mexico. © Edward Parker / WWF

Soil degraded and lost

When natural vegetation is cleared and when farmland is ploughed, the exposed topsoil is often blown away by wind or washed away by rain.

Erosion due to soy production, for example, sees Brazil lose 55 million tons of topsoil every year.¹This leads to reduced soil fertility and degraded land.

Other major crops that cause soil erosion include coffee, cassava, cotton, corn, palm oil, rice, sorghum, tea, tobacco, and wheat.²

Waterways clogged & polluted

Soil carried off in rain or irrigation water can lead to sedimentation of rivers, lakes and coastal areas.

The problem is exacerbated if there is no vegetation left along the banks of rivers and other watercourses to hold the soil.⁴

Sedimentation causes serious damage to freshwater and marine habitats, as well as the local communities that depend on on these habitats.

For example, people living in Xingu Indigenous Park in Brazil report declines in fish numbers. This trend is attributed to changes in the courses of waterways resulting from farming-related erosion and the silt deposition this causes.⁵

In Central America, plantation soil run-off ends up in the sea, where it affects the Meso American Reef.

It’s not just the eroded soil that is damaging: pesticides and fertilizers carried in rainwater and irrigation runoff can pollute waterways and harm wildlife.

Arable land destroyed

Land degradation stretches to about 30 % of the total global land area.⁶

The problem persists, with a reported loss rate of about 10 million hectares per year.

In reality, the situation may be much more worrying. Over the last 5 decades, increases in agricultural productivity have made it possible to produce more crops on the same amount of land.

But the problem is that because agricultural land is often degraded and almost useless, producers keep on moving to more productive land. Globally, the land used and abandoned in the last 50 years may be equal to the amount of land used today.³

Flooding increased

Erosion caused by deforestation can also lead to increased flooding. In banana plantations, for example, flooding occurs partly because of deforestation (soil is no longer there to absorb the water) and partly because of poorly constructed plantation drainage systems.

Pollution

Agriculture is the leading source of pollution in many countries.

Widespread contamination

The use of pesticides, fertilizers and other agrochemicals has increased hugely since the 1950s. For example, the amount of pesticide sprayed on fields has increased 26-fold over the past 50 years.

These chemicals don’t just stay on the fields they are applied to. Some application methods – such as pesticide spraying by aeroplane – lead to pollution of adjacent land, rivers or wetlands.

Due to inappropriate water management and irrigation technology, fertilizers and pesticides also commonly run-off from fields to adjacent rivers and lakes and contaminate groundwater sources. These chemicals eventually end up in the marine environment too.

Toxic pesticides

Pesticides often don’t just kill the target pest. Beneficial insects in and around the fields can be poisoned or killed, as can other animals eating poisoned insects. Pestcides can also kill soil microorganisms.

Pesticide pollution of rivers, lakes and wetlands also directly poisons freshwater species, as well as people.

Some pesticides are suspected of disrupting the hormone messaging systems of wildlife and people, and many can remain in the environment for generations.

Excess nutrients

Unlike pesticides, fertilizers are not directly toxic. However, their presence in freshwater and marine areas alters the nutrient system, and in consequence the species composition of specific ecosystems.

Their most dramatic effect is eutrophication – resulting in an explosive growth of algae due to excess nutrients. This depletes water of dissolved oxygen, which in turn can kill fish and other aquatic life.

Climate change

Farming practices, livestock, and clearing of land for agriculture are significant contributors to the build-up of greenhouse gases in the atmosphere.

Multiple sources of emissions

Agricultural practices are responsible for around 14% of global greenhouse gas emissions¹. Sources include fertilizers, livestock, wetland rice cultivation, manure management, burning of savanna and agricultural residues, and ploughing.

For example, rice production is one of the single-largest producers of methane, while the UN Food and Agriculture Organization (FAO) recently stated that the livestock sector alone is responsible for 18% of all greenhouse gas production.

In addition, the conversion of forests to agriculture – particularly in tropical Asia – accounts for a roughly similar percentage of greenhouse gas emissions as agriculture itself².

Genetic erosion

The replacement of traditional and local crops and farm animals with more genetically uniform, modern varieties has caused the genetic erosion of crops and livestock species around the world.

Lost genetic diversity

The widespread use of genetically uniform modern crop varieties has caused agricultural crops to lose about 75% of their genetic diversity in the last century.

Today, just 30 crops account for 90% of calories consumed by people, while 14 animal species account for 90% of all livestock production¹.

This lost genetic diversity reduces the potential for modern crops to adapt to, or be bred for, changing conditions – and so directly threatens long-term food security.