Despite the historical impacts of agriculture on biodiversity, some farm practices can enhance wildlife habitat and promote biodiversity. Direct benefits can accrue from maintaining populations of pollinator species, pest predators, and soil fauna and from preserving habitats such as wetlands, which conserve groundwater and help and protect against drought.
Agriculture has the potential to act both as a source and as a sink for several of the atmospheric greenhouse gases that are believed to be responsible for climatic changes. Agricultural activities relate to greenhouse gas concentrations in the following ways: (1) soils are an important natural source of and reservoir for carbon; (2) methane is emitted from livestock and liquid manure; (3) nitrous oxide is released from nitrogen fertilisers; and (4) carbon dioxide is released from the burning of fossil fuels in farming activities.
Nitrogen cycling in agricultural soils also generates nitrous oxide. This is probably the largest source of nitrous oxide from agriculture, and the least understood.
Because soil carbon fluxes will influence the overall greenhouse gas balance for agriculture, efforts to retain and increase levels of organic matter in soils can play a positive role in sequestering carbon and offsetting carbon dioxide emissions from agriculture and other sources.
In this regard, the increased use of practices such as conservation tillage and no-till are encouraging from a climate change, as well as soil quality, perspective. Other agricultural practices that may result in future net reduction of greenhouse gas emissions include reduced methane emissions from farm animals through improvements in feeding technology and feed additives improved crop yields, improved efficiency of manure use, decreased fossil fuel use and increased use of renewable fuel ethanol.
Agriculture is a direct consumer of energy for use in such activities as tilling, harvesting, heating, and ventilation. The main environmental concern related to energy use in the agriculture sector is the consumption of fossil fuels resulting in greenhouse gas emissions. Expanded production and use of renewable fuels such as ethanol could have environmental benefits — resulting in lower net carbon dioxide emissions, for example.
Reduced tillage, new herbicides with lower application rates, and genetic improvements in plants in terms of resistance to disease and lower fertiliser requirements all have implications for reducing energy use and achieving sustainability of agroecosystems.
Impact of Agriculture on Climate Change:
The impact of agriculture on the environment is often discussed merely in terms of pollution due to leaching of agrochemicals or to erosion of contaminated soil particles. As a matter of fact, however, more important environmental problems are due to the imbalance or the lack of closure of nutrient cycles and to the wrong choices made to this purpose.
The agricultural sector is a driving force in the gas emissions and land use effects thought to cause climate change. In addition to being a significant user of land and consumer of fossil fuel, agriculture contributes directly to greenhouse gas emissions through practices such as rice production and the raising of livestock.
Agriculture contributes to greenhouse gas increases through land use in- four main ways:
i. CO2 releases linked to deforestation;
ii. Methane releases from rice cultivation;
iii. Methane releases from enteric fermentation in cattle; and
iv. Nitrous oxide releases from fertiliser application.
The planet’s major changes to land cover since 1750 have resulted from deforestation in temperate regions: when forests and woodlands are cleared to make room for fields and pastures, the albedo of the affected area increases, which can result in either warming or cooling effects, depending on local conditions.
Deforestation also affects regional carbon re-uptake, which can result in increased concentrations of carbon dioxide, the dominant greenhouse gas. Land-clearing methods such as slash and burn compound these effects by burning bio- matter, which directly releases greenhouse gases and paniculate matter such as soot into the air.
Livestock and livestock-related activities such as deforestation and increasingly fuel- intensive farming practices are responsible for over 18% of human-made greenhouse gas emissions, including:
i. 9% of global carbon dioxide emissions;
ii. 35-40% of global methane emissions, chiefly due to enteric fermentation and manure; and
iii. 64% of global nitrous oxide emissions, chiefly due to fertiliser use.
Livestock activities also contribute disproportionately to laud-use effects, since crops such as corn and alfalfa are cultivated in order to feed the animals.
Effect of Modern Agriculture:
It makes use of hybrid seeds of selected and single crop variety, high-tech equipments and lots of energy subsidies in the form of fertilisers, pesticides and irrigation water. However, it also gave rise to several problematic off-shoots as discussed below:
i. Impacts related to High Yielding Varieties (HYV).
ii. Fertiliser related problems.
iii. Micronutrient imbalance.
iv. Nitrate pollution.
vi. Pesticides related problems.
vii. Creating resistance in pets and producing new pests (super pests—which have become immune to all types of pesticides).
viii. Death of non-target organisms.
ix. Biological magnification: Many of the pesticides are non-biodegradable and keep on accumulating in the food chain, a process called biological magnification.
x. Waterlogging: Waterlogging occurs when the water table rises and eventually approaches the soil surface rendering the root zone unsuitable for crop growth. Excessive wetting and waterlogging are generally accompanied by oxygen deficiency because most pores are filled with water and the soil-air gets depleted.
xi. Salinity problem: This term is commonly used to refer to the soluble salt content of the soil. When soil salinity increases to harmful levels, plants are subject to reduce osmotic potential of the soil solution and to toxicity of specific ions such as chlorine and sodium.