Brazil's Cerrado is the world's most biodiverse tropical savanna, covering approximately 2 million km2 across central Brazil. It is home to over 10 000 plan...

(a)(i) Percentage of global greenhouse gas emissions from agriculture: [1]

Approximately 26% of global greenhouse gas emissions come from agriculture, as stated in the central box of Fig. 1 [1].

(a)(ii) One greenhouse gas produced by cattle farming: [1]

Methane (CH\(_4\)) [1]. Methane is produced during the digestive process (enteric fermentation) in the stomachs of cattle and is also released from decomposing manure. Nitrous oxide (N\(_2\)O) from manure is also acceptable.

(b) Three ways agriculture produces greenhouse gas emissions (from Fig. 1): [3]

1. Livestock such as cattle produce methane through digestion (enteric fermentation) and from the decomposition of manure [1]. Fig. 1 shows this under the "Livestock" branch with sub-categories for cattle digestion (CH\(_4\)) and manure (CH\(_4\) and N\(_2\)O).
2. Clearing land by burning vegetation releases carbon dioxide directly into the atmosphere, and disturbed soil also releases stored carbon as CO\(_2\) [1]. Fig. 1 shows this under "Land clearing" with sub-categories for burning and soil carbon release.
3. Rice paddies produce methane because waterlogged soil creates anaerobic (oxygen-free) conditions where bacteria decompose organic matter and generate methane as a by-product [1]. This is shown in Fig. 1 under the "Rice paddies" branch.

(c) How clearing native Cerrado vegetation contributes to climate change: [3]

1. Trees and other vegetation in the Cerrado store large amounts of carbon in their biomass (trunks, branches, roots, leaves). This is known as a carbon sink [1].
2. When this vegetation is cleared and burned, the stored carbon is released as carbon dioxide (CO\(_2\)) into the atmosphere, adding to the greenhouse effect [1].
3. The removal of vegetation also reduces the number of plants available to absorb CO\(_2\) through photosynthesis, so less carbon dioxide is removed from the atmosphere each year. The land changes from a carbon sink to a carbon source [1].

(d) Changes in land use in the study area between 2000 and 2020 (from Table 1): [2]

Native savanna vegetation decreased significantly, falling from 280 km\(^2\) to 145 km\(^2\) - a loss of 135 km\(^2\), nearly half the original area [1]. This lost vegetation was replaced primarily by agriculture: soybean cropland more than doubled from 95 km\(^2\) to 195 km\(^2\), and cattle pasture increased from 110 km\(^2\) to 140 km\(^2\). Urban and other land uses grew modestly from 15 km\(^2\) to 20 km\(^2\) [1]. The total area remains 500 km\(^2\), confirming that the agricultural expansion directly replaced native savanna.

(e) Two reasons why farmers continue to clear vegetation despite the environmental consequences: [2]

1. Farming soybeans and cattle is highly profitable, and global demand for these products continues to grow, creating strong economic incentives to expand production [1].
2. Land in the Cerrado is relatively cheap to purchase and clear compared to other regions, and farmers may have limited alternative employment opportunities [1].

(f) Three methods to reduce greenhouse gas emissions from agriculture while allowing food production: [3]

1. Improving cattle feed and breeding to reduce the amount of methane each animal produces during digestion. Research shows that feed additives can cut methane output by up to 30% [1].
2. Practising agroforestry, where trees are planted alongside crops or pasture. The trees absorb CO\(_2\) through photosynthesis while still allowing food production on the same land [1].
3. Using no-till or reduced-tillage farming methods that keep carbon locked in the soil rather than releasing it. Ploughing exposes organic matter to air and accelerates decomposition; no-till avoids this [1].

(g) Why reducing agricultural emissions is more difficult than reducing electricity emissions: [3]

1. Agriculture involves millions of individual farms spread across vast areas, making it very difficult to monitor, measure, and regulate emissions from every source. A coal power station is a single point source that can be controlled directly [1].
2. People need food to survive, so agricultural production cannot simply be stopped or drastically reduced in the way that a coal-fired power station can be replaced by a wind farm [1].
3. Many agricultural emissions come from biological processes (cattle digestion, soil bacteria producing N\(_2\)O, rice paddy decomposition) that cannot be eliminated by switching technology. In electricity generation, fossil fuels can simply be replaced with renewables [1].

(h) Two ways climate change could reduce crop yields in tropical regions: [2]

1. Higher temperatures increase the rate of evaporation from soil, leading to drought stress in crops and reducing the amount of water available for plant growth during critical stages [1].
2. Changes in rainfall patterns may cause floods or droughts at critical growing stages (such as germination or flowering), damaging or destroying crops and reducing harvests [1].