Causes: Land use
Causes
- A brief history of climate change: who knew what, when
- What causes climate change?
- Would the climate be warming without humans?
- Is it just a cycle? (Earth’s wobbly orbit)
- Sunspots & solar activity
- Land use: agriculture & cities
- Volcanoes
- Ocean currents
- Black carbon & ash
- Albedo effect
- Hydrogen
- Greenhouse gases & how they work
- – Carbon dioxide & the carbon cycle
- – Methane: biogenic (mostly cows) & ‘natural’ gas
- – Nitrous oxide (mostly agriculture)
- – Clouds & water vapour
- – Ozone
- – Man-made industrial chemicals
- – Aerosol pollution
- How to start an Ice Age!
- What’s in a name?
Home > Climate wiki > What causes climate change? > Land use: agriculture
Land use: agriculture and cities
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
- 50% of the world’s habitable land is used for agriculture (Figs. 1 & 2), 1% of land is used for urban development and infrastructure, and residents of just 100 cities account for 20% of humanity’s overall carbon footprint.
- 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 accounts 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 assumption that the so called ‘CO2 fertilisation effect’ leads to more plant growth is inaccurate as it does not factor in the loss of nutritional value and ignores the effect of heat.
- 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.
Causes
- A brief history of climate change: who knew what, when
- What causes climate change?
- Would the climate be warming without humans?
- Is it just a cycle? (Earth’s wobbly orbit)
- Sunspots & solar activity
- Land use: agriculture & cities
- Volcanoes
- Ocean currents
- Black carbon & ash
- Albedo effect
- Hydrogen
- Greenhouse gases & how they work
- – Carbon dioxide & the carbon cycle
- – Methane: biogenic (mostly cows) & ‘natural’ gas
- – Nitrous oxide (mostly agriculture)
- – Clouds & water vapour
- – Ozone
- – Man-made industrial chemicals
- – Aerosol pollution
- How to start an Ice Age!
- What’s in a name?
Home > Climate wiki > What causes climate change? > Land use: agriculture
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
- 50% of the world’s habitable land is used for agriculture (Figs. 1 & 2), 1% of land is used for urban development and infrastructure, and residents of just 100 cities account for 20% of humanity’s overall carbon footprint.
- 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 accounts 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 assumption that the so called ‘CO2 fertilisation effect’ leads to more plant growth is inaccurate as it does not factor in the loss of nutritional value and ignores the effect of heat.
- 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.
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Fig. 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)
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Summary quote as follows: see the full 2025 report
- 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).
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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 spread. 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 slight cooling, thereby maintaining a relatively stable temperature until the Industrial Revolution. At that point, burning fossils fuels for energy began releasing equally huge quantities of greenhouse gasses into the atmosphere.
The Industrial Revolution also led to industrial-scale agriculture and horticulture. Enabled by science and technology, some 25% of the Earth’s natural landscapes has since been converted into monoculture crops enhanced by oil and gas products: fertilisers, and pesticides and herbicides engineered to eradicate all competing species. This has resulted in relatively cheap plentiful food with little to no resiliency in the face of climate change. As the IPCC has pointed out, industrial agriculture has simultaneously destroyed the life-supporting ecosystem services—including clean water and a liveable climate—necessary for the planet to remain habitable.
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Video 1: The effect of land use change across Aotearoa since the arrival of humans: Parliamentary Commissioner for the Environment.
In effect, industrial agriculture is a giant Ponzi scheme that’s now catching up with us.
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Image: Our World in Data
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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 food crops—are structurally weaker, making them more prone to higher and hotter winds (increasing evapotranspiration) of the type that commonly occurs in Canterbury. Today, orchards and forests may not reach maturity before their tolerance for increasing temperatures is exceeded.Food plants are decreasing in nutritional values (see also Video 2).
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Video 2: Physicist and science educator Dr. Derek Muller explains what’s causing our food to become less nutritious.
- Reliable growing seasons are becoming increasingly difficult in a rapidly warming climate
- 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:
- Some mature natural forests are able to sequester increased CO2, hence why native forests need to be protected.
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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.
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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. This does not mean agriculture is ‘cooling’ the planet; the same effect of trees in cities keeps cities cooler (Fig. 4).
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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.
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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.
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Fig. 4. The ‘heat-island’ effect of cities and urban areas.
Residents of just 100 cities account for 20 percent of humanity’s overall carbon footprint. – McCarthey et al
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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More information
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Clean ice and snow have a very high albedo, that is, they reflect up to 90% of solar radiation back into space The ocean is much darker, so it has a very low albedo, reflecting only about 6% of the incoming solar radiation and absorbing the other 94%, warming it much faster than the snow and ice (Fig. 6).As more ice forms, the water is cooler, leading to more ice forming, and so on, in a feedback effect. However,
Recent global temperature surge intensified by record-low planetary albedo – Science, 05 Dec. 2024 (Figs. 7 & 8)
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Image: Nathan Kurtz / NASA
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Image: Duspayev et al; Earth’s Sea Ice Radiative Effect from 1980 to 2023
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Image: Eliot Jaboson; data: NASA
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The term ‘climate forcing’ comes from ‘radiative forcing’ or RF, which is the difference between the amount of solar energy reaching Earth’s atmosphere and the amount that escapes. If more solar energy escapes than arrives, the planet cools. Conversely, if less energy escapes than gets in, the planet warms.
Click here to learn about the main forcings and how they work (links to a page on this site).
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When we perspire (sweat) the moisture evaporates into the air, cooling us down. How much and how quickly it evaporates depends on how much water is already in the air (humidity) and how warm this air is.Water also evaporates from any other objects that have water on their surface: a glass of cold water, the ground, the ocean, soil and rocks. Warmer air can ‘carry’ around 7% more water for every degree warmer it gets. As the air cools, the water is released.Transpiration is how water moves within plants and releases water vapour through stomata in vascula plants (trees and most plants) or phyllids in non-vacsular plants (algae, mosses etc.).Evapotranspiration is the term used to describe the combined loss of water from both plants and everything else around them including the soils. Some of this water vapour rising from the ground may be intercepted by
trees as it rises and cools. Rainforests produce their own rain because there is so much evapotranspiration.If there are no trees, the moisture rises high into the air and can be carried long distances before it falls as precipitation. This is why, when a rainforest is cut down, less rain falls in the area.As global temperatures rise, the air can carry more water (around 7% more water for every degree of warming). So, evermore evapotranspiration takes water from soils and low lying plants including food crops. This can quickly lead to a drought.
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- 2026: Dang et al; Respiration-Induced Weakening of Land Sink Contributed to the Largest CO2 Increase Global Change Biology 32 |4: 01 April
- 2026: Columbia Climate School; New Research Indicates That in the Future, Trees May Store Less Carbon Than Expected
- 2026: Mongabay; Loopholes undermine palm oil industry’s antideforestation pledges, 27 May
- 2026: Wunderling et al; Deforestation-induced drying lowers Amazon climate threshold, Nature 06 May (open access)
- 2026: Cao et al; Spatially explicit global assessment of cropland greenhouse gas emissions circa 2020, Nature Climate Change 13 Feb. (Open access)
- 2025: Adbo et al; Conventional agriculture increases global warming while decreasing system sustainability, Nature Climate Change 15 pp110-116
- 2025: Friedlingstein et al; Emerging climate impact on carbon sinks in a consolidated carbon budget, Nature, 12 November
- 2025: Plants losing appetite for carbon dioxide amid effects of warming climate, The Guardian
- 2025: Australian tropical rainforest trees switch in world first from carbon sink to emissions source, The Guardian
- 2025: UNFAO;
- 2025: Sadai et al; Estimating the sea level rise responsibility of industrial carbon producers, Environmental Research Letters 20 | 4 (Open access)
- 2024: Climate Commission issues a yellow card on emissions progress (Lack of policy to reduce livestock emissions) – Newsroom
- 2022: Pedersen et al; Regenerative living cities and the urban climate–biodiversity–wellbeing nexus, Nature Climate Change 12 pp601-604
- 2022: Cabon et al; Cross-biome synthesis of source versus sink limits to tree growth, Science 376 | 6594 pp758-761
- 2022: Viglione: What does the world’s reliance on fertilisers mean for climate change? Carbon Brief
- Our Land – Chapter 3: Our activities and their effects, NZ Ministry for the Environment
- Statistics New Zealand: Agricultural and horticultural land use
- Heat Island Effect: National Geographic explainer
- 2020 IPCC: Climate Change and Land Use; summary for policymakers
- 2020 IPCC: Climate Change and Land Use; all chapters
- 2020: Sciblogs NZ: Why higher carbon dioxide levels aren’t good news, even if some plants grow faster
- 2020: Hubau et al; Asynchronous carbon sink saturation in African and Amazonian tropical forests, Nature 579, 80–87
- 2020: Shi et al; The age distribution of global soil carbon inferred from radiocarbon measurements, Nature Geoscience 13, 555-559
- 2020: Du et al; Global patterns of terrestrial nitrogen and phosphorus limitation, Nature Geoscience 13, 221–226
- 2019 World Economic Forum; Oceans absorb almost 1/3 of global CO2 emissions, but at what cost?
- 2019: Carbon Brief, In-depth Q&A: The IPCC’s special report on climate change and land
- 2019: National Geographic: Ocean acidification explained
- 2018: Ministry for Primary Industries: Report of the Biological Emissions Reference Group (BERG)
- 2018: Dong et al; Effects of Elevated CO2 on Nutritional Quality of Vegetables: A Review, Frontiers in Plant Science Aug. 2018
- 2018: Moran et al; Carbon footprints of 13 000 cities, Environmental Research Letters 13/6 pp
- Website affiliated with the paper: City Carbon Footprints
- Scientific American article about this research: Here’s How Much Cities Contribute to the World’s Carbon Footprint
- 2017: DeVries et al; Recent increase in oceanic carbon uptake driven by weaker upper-ocean overturning, Nature 542, 216
- Carbon Brief article on the above: Scientists solve ocean ‘carbon sink’ puzzle
- 2016: Zhang; The Impacts of Land-Use and Land-Cover Change on Tropospheric Temperatures at Global and Regional Scales, American Meterological Sociey: Earth Interactions.
- 2014 IPCC: Chapter 8 Urban Areas in Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects.
- 2013 IPCC: Anthropogenic and natural radiative forcing. Climate Change 2013: The Physical Science Basis, T. F. Stocker et al., Eds., Cambridge University Press, 659–740.
- 2010: McCarthey et al; Climate change in cities due to global warming and urban effects, Geophyscial Research Letters 37/9