1.15 tropical rainforests the water cycle

  1. Describe the human threats to the TRF (i.e. why is it destroyed)?

One of the most major human threats to the TRF is deforestation. This was mainly due to agriculture and the land being made arable amd using it for farming, but there have also been some cases of deforestation of TRF being cut down for commercial amd residential buildings as well, if there is an urban are nearby that is expanding. Also through wildfires and droughts caused by global warming. Damming of rivers can also cause droughts.

  1. Using figs 3 and 4 describe how the water cycle of a TRF is affected by deforestation?

Less water is being moved around by evapotranspiration and absorption, with less water moving around inside the plant as well, however there will also be more infiltration and percolation due to there being less interception and stem flow. This will result in greater surface runoff, as there will be more water in the soil and less in the atmosphere, allowing the soil to become saturated very quickly and therefore create more surface runoff. This means that there will need to be more money invested in methods to manage the flooding that will occur once there is too much water on the surface, which will put pressure on councils. There will also be political pressure from political parties who will be against deforestation which could start conflicts. It could also potentially cause more extreme weather as the climate would be thrown out by the sudden lack of evapotranspiration and the water moving around more due to surface runoff

  1. Use the following factors to guide your answer?

 

  1. Social

  2. Economic

  3. Environmental

Atmosphere becomes less humid as evapotranspiration is reduced

With few trees most rainfall reaches the ground immediately compacting the soil and encouraging overland flow

Exposed to the sun, the soil will become very dry and vulnerable to erosion

Few trees remain so very little interception of rainfall or evaporation off leaves. Transpiration will be virtually zero

Rates of runoff will increase with an increased risk of flooding

  1. Political

 

  1. THINK SPATIALLY, see if you can think of global effects

It could cause issues with the amount of oxygen being produced, as they make 28% of the worlds oxygen, and there may be issues with more soil erosion letting more carbon into the atmosphere

  1. How can the exploitation and management of the rainforest be made more sustainable to reduce the impact on the Carbon and water cycles

 

  1. Carbon

If carbon is going to be released into the atmosphere by something happening to the TRF then we should offset the same amount of carbon in the area to prevent unbalance in the carbon cycle

  1. Water

Replant any trees that are cut down, on to another part of the forest to help reduce the amount of flooding due to water not being intercepted or reabsorbed and released into the atmosphere by evapotranspiration

  1. “Assess the impact of deforestation on the water cycle in tropical rainforests.” (9 marks)

Marking Guidance

  • Level 1 (1–3 marks): Basic description of deforestation and simple statements about reduced rainfall or increased runoff.

  • Level 2 (4–6 marks): Clear explanation of processes (e.g., reduced evapotranspiration, interception loss, increased surface runoff, soil erosion).

  • Level 3 (7–9 marks): Detailed assessment with links to wider impacts (regional climate change, feedback loops, flooding risk), possibly supported by examples or data.