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Causes: Land use


Home > Climate wiki > What causes Earth’s climate to change? > Land use

Summary

Livestock and humans now account for nearly 96% of all mammal biomass on Earth, and more species are threatened with extinction than ever before in human history.  – IPCC-IPBES, 2021

Fifty percent of the world’s habitable land is used for agriculture (Fig. 1); 1% is used for urban development and infrastructure, and residents of just 100 cities account for 20% of humanity’s overall carbon footprint.

Figure 1: Scroll over the graph to show more details. Click ‘Change country/region’ in the upper left to select more detailed data. Graph: Our World in Data

The expansion of agriculture and forestry and adding agrichemicals to them to increase productivity have rapidly escalated greenhouse gas emissions including methane and nitrous oxide, loss of biodiversity and destruction of life-supporting ecosystem services.

Globally, agriculture uses ~70% of global fresh-water and in 2020 accounted for ~23% of greenhouse gas emissions

Across Aotearoa, agriculture and horticulture together produce more than 50% of our greenhouse gas emissions.

Soils contain more carbon than the atmosphere and plants combined, but conventional agricultural soils are vanishing more than 100 times faster than new soils are forming.

The UN Food and Agriculture Organization (FAO) show a 17% increase in food-related emissions since 1990. While land-use change contributed the largest portions of emissions, the:

…data also showed that factors, such as transport, storage and food preparation unrelated to onfarm activities and land-use changes were also growing, accounting for more than half of the carbon emissions from agri-food systems.

Regenerative living cities can create an urban climate–biodiversity–wellbeing nexus.

What’s covered on this page:

The Agricultural Revolution

The transition of many human cultures from hunting and gathering to agriculture began ~12,000 to 15,000 years ago, around the time the last glacial maximum ended. By ~11,750 years ago the global climate began stabilising enough for agriculture to be a reliable source of food. By 9,000 years ago agriculture was common in many places. At the same time, the Earth’s climate was slowly moving into a natural cooling phase.

Greenhouse gas emissions from agriculture have been credited with offsetting this very gradual cooling, thereby maintaining a relatively stable temperature until the Industrial Revolution. Burning fossils fuels for energy released staggering quantities of greenhouse gases into the atmosphere.

The Industrial Revolution also led to industrial-scale agriculture and horticulture, resulting in an equally staggering increase in greenhouse gas emissions:

  • Global agrifood systems emissions reached 16.5 billion tonnes of carbon dioxide equivalent (Gt CO2eq) in 2023, up 21 percent since 2001. Their share in total emissions fell from 38 to 32 percent in 2023.
  • Farm-gate emissions from crop and livestock amounted to 8.1 Gt CO2eq in 2023, or 49 percent of agrifood systems emissions, marking a 17 percent increase since 2001.
  • Pre and post agricultural production emissions rose by 33 percent since 2001 to 5.2 Gt CO2eq in 2023, accounting for 32 percent of agrifood systems emissions. Emissions from manufacturing, transport, packaging, retail, and household consumption grew by about 80 percent.
  • Land-use change emissions declined 6 percent to 3.2 Gt CO2eq since 2021, accounting for 19 percent of agrifood systems emissions.
  • In 2023, livestock emissions (4.3 Gt CO2eq) were the largest single component, followed by deforestation (2.8 Gt CO2eq), and packaging, transport and retail (1.4 Gt CO2eq).
  • In 2023, emissions were largest in Asia (7.1 Gt CO2eq), followed by the Americas (4.8 Gt CO2eq), Africa (2.4 Gt CO2eq), Europe (1.9 Gt CO2eq) and Oceania (0.4 Gt CO2eq). Since 2001, emissions increased in Asia (+53 percent), Africa (+17 percent), and the Americas (+7 percent), but declined in Europe (−6 percent) and Oceania (−19 percent).
  • The global emissions intensity of agricultural production in 2023 was 1.9 kg CO2eq per international dollar, down 25 percent from 2001. It declined in all regions, from −21 percent in Europe to −31 percent in Oceania.
  • Per capita agrifood systems emissions fell by 6 percent since 2001 to 2.0 t CO2eq/cap in 2023. Oceania remained the highest emitter (8.1 t CO2eq/cap), followed by the Americas (4.6 t CO2eq/cap), Europe (2.5 t CO2eq/cap), Africa (1.6 t CO2eq/cap) and Asia (1.5 t CO2eq/cap).

– FAO 2025 Greenhouse gas emissions from agriculture

Enabled by science and technology, some 25% of the Earth’s natural landscapes has since been converted into monoculture crops enabled by the bi-products of oil and gas: fertilisers including nitrogen (Fig. 2), pesticides, herbicides, and fungicides engineered to eradicate all competing species. Along with advances in genetics this revolution resulted in relatively cheap plentiful food with little to no resiliency in the face of climate change. As the IPCC  pointed out in 2020, industrial agriculture has simultaneously destroyed the life-supporting ecosystem services—including clean water and a liveable climate—necessary for the planet to remain habitable.

In effect, the agricutural revolution has been a giant Ponzi scheme that’s now catching up with us.

Nitrogen pollution one of the most pressing pollution problems facing humanity
Figure 2: Nitrogen pollution contributes to the triple planetary crisis of climate change, nature and biodiversity loss, and pollution and waste.
Figure 3: Image: Our World in Data

Doesn’t more CO2 mean more plant food?

The speeding-up of photosynthesis—known as ‘CO2 fertilisation’—is well-known to be an important consequence of higher atmospheric CO2 concentrations, along with increased water use efficiency. As CO2 in the atmosphere increases, in theory, plants don’t lose as much water through their leaves because the number of stoma decreases. So drier conditions shouldn’t have such a large impact.
 
However, reality trumps theory. Fast growing plants—including many food crops—become structurally weaker, making them more prone to higher and hotter winds, which leads to increasing evapotranspiration of the type that commonly occurs in Canterbury. Andf ood plants are also decreasing in their nutritional values (Video 2).

Reliable growing seasons are becoming increasingly difficult in a rapidly warming climate. Today, orchards and forests may not reach maturity before their tolerance for increasing temperatures is exceeded.

Some trees are increasing photosynthesis but this is not leading to wood growth, and often results in CO2 being released through the roots and soil:

However, some mature natural forests are able to sequester increased CO2, hence why our native forests need to be protected.

Burning tropical rainforests for agriculture

Research shows that the ability of intact tropical forests to remove CO2 from the atmosphere reached its peak in the 1990s and has since been in decline. Meanwhile, millions of hectares of tropical rainforest continue to be burned specifically to grow meat, soya, and palm oil to fed livestock that goes to overseas buyers including McDonald’s and Burger King, which also buy vast quantities of beef from Brazil. Along with Kentucky Fried Chicken, McDonald’s and Burger King also serve chicken fed a diet of soya from Brazil.

 

Isn’t agriculture cooling the atmosphere?

Due to the albedo effect and short term cooling from evapotranspiration, changes in land use have caused a slight decrease in the average temperature of the troposphere over some farmlands, but only if enough water is available. This does not mean agriculture is ‘cooling’ the planet; the same effect of trees in cities keeps cities cooler (Fig. 4).

 
Fig. 4. The ‘heat-island’ effect of cities and urban areas.

Agricultural lands do not store nearly as much water in the plants and crucially, their soils. And equally crucially, industrial-scale agriculture such as dairy farming in Canterbury is leading to the rapid loss of soils. Soils contain more carbon than the atmosphere and vegetation combined. Losing soils is worse than losing forests.

Agricultural soils are becoming sources of carbon emissions rather than carbon sinks.  – IPCC 5th Assessment Report.

What about urban areas?

Warming and extreme heat events due to urbanisation and increased energy consumption are simulated to be as large as the impact of doubled CO2 in some regions. – McCarthey et al

Approximately 1% of the surface of the Earth is classed as ‘urban’ , ie, cities and infrastructure including roads. The ‘heat-island’ effect of cities has been recognised since the late 1800s and well-studied since then (Fig. 4). On the whole, modern cities create vast areas of surfaces that are impermeable to rain: concrete pavement, bitumen roads, and rooftops. Waste heat from powering buildings adds to the ambient temperatures. Dark bitumen surfaces and concrete retain daytime heat. The end result is that cities are 1–3°C warmer on average—and as much as 12°C warmer in the evening—than surrounding areas.
 
 

Residents of just 100 cities account for 20 percent of humanity’s overall carbon footprint – op. cit.

In terms of how much cities contribute to climate change, it’s not so much the land area or use that contributes, as the activities and consumption of the people that inhabit them. This is our ‘carbon footprint’. Urban dwellers almost exclusively depend upon food grown by industrial agricultural systems and for carbon-intensive manufacturing, buildings and infrastructure manufactured by intensive carbon-emitting processes, and linked and serviced by equally intensive carbon-emitting transport systems.

Our consumer driven society demands cheap, conveniently available food and goods, the latest tech and modern conveniences, and fast easy transport. This drives all aspects of land use including agriculture, mining, urban development and the infrastructure to support these demands. This in turn drives climate change.

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