First published 2023
Agriculture is the world’s second largest emitter of greenhouse gasses and is responsible for 13% of total global emissions. It is one of the biggest contributors to biodiversity loss and is due to increased demand for food from an exponentially expanding population. By converting natural habitats and ecosystems into intensely managed farmland to create monocultures of crops, the index of species diversity is mostly reduced. Businesses amplify this negative impact through energy use, transport and waste which further reduces global biodiversity and heavily contributes to greenhouse gas emissions.
By filling in ponds and draining marshlands, more farmland space is created to grow crops. By eradicating wetlands in this way, inland aquatic ecosystems severely decline, leading to major habitat loss for fish, reptiles and amphibians. Habitats provide food and shelter for organisms meaning this loss increases competition among species with similar ecological niches; therefore not all of them survive so species diversity decreases. Farmers can reduce this impact by leaving wet corners of fields rather than draining them and maintaining existing ponds. In 2013, a study of 94 ponds across farmlands in Spain was carried out which concluded that natural ponds within farms increase species richness and diversity compared to artificial ponds but still more so than no ponds.
Additionally, the increasing use of inorganic chemical fertilisers and pesticides indirectly causes a decrease in the species diversity within farmlands. Whilst the use of fertilisers aims to improve the supply of nutrients and promote plant growth, fertiliser runoff can trigger a process called eutrophication. This starts when the nutrient rich fertilisers (containing nitrates and phosphates) are washed into rivers or lakes. These nutrients are taken in by phytoplankton (algae) which grow and reproduce quickly, forming a thick bloom layer on the water’s surface. This prevents sunlight reaching photosynthesising plants underwater which therefore die. The algae will die when it runs out of nutrients from the water. Then bacteria decompose the dead algae, releasing nutrients back into the water. As the bacteria divide and grow, they consume oxygen causing the water to become anoxic. This causes organisms such as fish to die, which disrupts the aquatic food chain, causing lower biodiversity levels. However interestingly, trees can act as natural water filters. As their roots absorb rainwater to minimize the amount of runoff entering rivers and lakes, minimising the effect of eutrophication.
Although they increase the yield of crops, the use of pesticides and herbicides kill insects and weeds respectively which may threaten the survival of the farmers’ plants. To manage this, farmers could use biological control such as the release of parasitic wasps to control aphids (a plant pest which removes nutrients from the plant) or the farmer could use organic rather than inorganic fertilizers.
Furthermore, a lack of crop rotation causes less nutrients in the soil, an increase in soil erosion, and an increase in plant diseases and pests. Crop rotation is the systematic planting of different crops in a particular order over several years in the same growing space. By rotating crops, different nutrients favoured by different plants are absorbed from the soil, preventing any severe lack of one type of nutrient in a certain area of soil. To prevent the negative effects, farmers could use crop rotation that includes a nitrogen-fixing crop, rather than fertilisers, which would improve soil fertility. This would therefore increase the variety of nutrient species and microorganisms underground, leading to an overall increase in biodiversity.
Alternatively, a positive impact of increased agriculture on biodiversity is that soil biodiversity can be increased by intensive farming, Soils form complex ecosystems that make farming possible because there are millions of both microorganisms (such as bacteria and fungi) and macroorganisms (such as worms, mites, ants and spiders) that live in soil. Nutrients provided by fertilisers and growing plants feed organisms. When they eat and dig underground burrowing organisms, like earthworms and termites mix the upper layers, redistribute nutrients and increase the amount of water absorbed by the soil and therefore by the plant. This demonstrates interdependence between plants and organisms within agriculture. Furthermore, some macroorganisms are critical to local farming techniques. For example, Farmers in Burkina Faso and in other areas of West Africa encourage termites to live and burrow in their farm plots because they improve the soil.
To conclude, the trade-off between sustaining a large population agriculturally and maintaining global biodiversity remains a critical challenge. However farmers collectively can reduce the impact of agriculture on biodiversity through less intensive farming techniques and conservation of naturally occurring species.
Links
https://www.wri.org/insights/everything-you-need-know-about-agricultural-emissions
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