Food production from plants and animals impacts the natural environment in various ways. It affects things like land and water usage, the natural balance of greenhouse gas emissions and sequestration, and biodiversity conservation.

At a global level, agriculture utilises 37% of all land. Of this proportion only a third is arable and suitable for growing crops, with a much smaller proportion able to support continuous cropping. The remaining two thirds of non-arable land is utilised for grazing with livestock, many of which are ruminant species. This livestock grazing enables the conversion of raw plant material inedible by humans into high quality, nutrient dense human food. 

Around 71% of the earth’s surface is covered by water, mostly in oceans, with 29% land. The world’s total land area is about 13 billion hectares (ha), excluding Antarctica and inland waters. Of this, about a third (4.8 billion ha) is agricultural land, with forest and other lands (such as deserts, urban areas, and infrastructure) occupying the rest. 

At a global scale, only a third of agricultural land is arable (that is, suitable for growing crops), with a much smaller proportion capable of supporting continuous cropping. The remaining two thirds (3.2 million ha), is non-arable pastureland utilised for livestock grazing. Importantly, these proportions of land classes vary widely by region due to climate, topography and human settlement. 

So, the actual and optimal land use at any place, together with its environmental interaction, must be considered in its localised context.

Food production for plants and animals

Food production from both plants and animals has various impacts on the environment including land and water usage, greenhouse gas emissions, impact on biodiversity and water systems. Ruminant livestock species such as sheep, goats and cattle, have the unique ability to convert material that is inedible by humans into high quality, nutrient dense human food, providing a vital service in upcycling human-inedible pasture and herbage for the global food supply system. 

Grazing by animals also stimulates plant growth which, in turn, relies on photosynthesis capturing atmospheric CO2 into fixed plant carbohydrates. This natural system efficiently transfers carbon from the atmosphere to growing plant material above- and below-ground. Grazed plant material is utilised by livestock for their bodily maintenance, and for milk and meat production. Wastes from this biological process are deposited on the pasture in the form of urine and manure.

Another by-product of livestock grazing by ruminants is methane. This short-lived greenhouse gas is recycled back into CO2 by soil some microbes and in the atmosphere, completing the natural biogenic carbon cycle.

Within the pasture, carbon transferred though plant roots to the soil is exchanged for needed nutrients with beneficial soil microbes (fungi and bacteria) which form a natural symbiotic system essential for healthy soil and plant production. 

Historically, it is believed that megafauna and ruminant species such as bison in USA and many other wild ruminant grazers were instrumental in the formation of deep, highly fertile soils. This is evidenced in today’s savannah and rangelands regions with grass, shrubs and trees being maintained in balance by grazing herds in high densities that continuously move across the landscape. The expansion of domesticated livestock areas means the amount of carbon sequestered in soil and/or returned to the atmosphere through grazing, tillage or erosion is now dependent on the management practices of farmers and graziers.

Intensive and unmanaged farming and grazing practices have often resulted in substantial soil and ecosystem degradation. The recent reintroduction of regenerative agricultural practices is helping restore carbon in soils and on-farm vegetation which has global potential to mitigate industrial atmospheric carbon increases. There is more than double the amount of carbon stored in soils than in the atmosphere or in vegetation.

Soil is the most biodiverse singular habitat with improved soil health the key to increased biodiversity above and below ground, to greater water capture (thereby mitigating the warming potential of water vapour in the atmosphere), of increased high quality human food production and of reversing current climate change trends.

Benefits and impacts of livestock grazing

There is clear evidence that well-managed livestock grazing, including long rest pasture periods, promotes biodiversity recovery and the health of the soil microbiome, with flow-on benefits for the entire food system. 

Intensive livestock systems also have environmental impacts. However, understanding the local context and management is important in evaluating and mitigating such impacts.  As with poor cropping or grazing management intensive dairies, feedlots and non-ruminant livestock systems can clearly lead to environmental damage.

Nevertheless, such systems can be important in complementing grazed systems by enabling livestock to be carried through seasons where plant growth is low or non-existent, or pastures would be damaged by pugging or overgrazing.

Diet and effluent of animals

Further considerations relate to the diets fed, which often include high proportions of human inedible food and crop by-products, adding nutrients contained in these products back into the human food chain, reducing waste and waste generated emissions. It is estimated that 86% of all livestock feed is human inedible material.

Effective utilisation of manure and effluent is also central to mitigating environmental damage and often central to a circular nutrient supply chain. However, the net impacts of such circularity among different sectors of food production are not always captured in biophysical models and sustainability frameworks.

A final consideration in providing adequate nutrition for a projected 10 billion global population in concert with improving environmental impact is the critical impact of productivity.

All animals prioritise food intake to basic maintenance, with intake beyond this utilised in growth or production such as meat, milk or wool. 

As maintenance needs are fixed, the higher the intake the greater the percentage of food that is utilised in producing meat, milk or fibre. Consequently, for grazed and intensive systems, higher productivity increases efficiency and reduces feed utilised per unit of production. Practical application of continuing scientific advances in genetics, animal health and management systems is delivering improved human food and environmental outcomes.