Rainforests and savannas contain 70% of the world’s plants and are critical
to the health of our planet. A new £1.6m international project involving
researchers from the Leeds Earth and Biosphere Institute is looking at the
impact of global warming on these sensitive areas.
The researchers think we may be at the start of a vicious cycle, where global
warming causes the rainforests to shrink, so increasing the amount of carbon in
the atmosphere, raising the earth’s temperature and magnifying the impact on the
rainforests.
Heading the work at Leeds is Professor of Earth System Science, Jon Lloyd: “The
two major vegetation systems in the tropics are rainforest and savanna. As it
gets warmer and drier the rainforest gets invaded by savanna, which has fewer
trees and holds less carbon in the soil. Savanna also doesn’t recycle water in
the same way as rainforest, so the carbon loss from the savanna is greater and
the atmosphere becomes drier.”
The researchers want to find out under what conditions rainforest and savanna
are able to thrive. It’s not a simple question of rainfall: areas in Africa with
1800mm of rainfall a year are rainforest; in South America, areas with the same
rainfall are savanna.
Other issues such as soils, fertility and drainage must play a part, the
researchers believe. They will make measurements in Africa, Australia and South
America, focusing on ‘zones of tension’ where rainforest and savanna currently
grow side by side.
Using these measurements, detailed computer models will be created to look at
the impact of changes in tropical vegetation on the Earth system in terms of
carbon emissions, temperature and rainfall. These changes will then be fed back
into the models to determine their cumulative impact and ultimately predict
global climate change.
The researchers hope to complete their calculations within five years. If this
shows that the level of carbon in the atmosphere is set to increase beyond
current estimates it could force a change in international targets for reducing
carbon emissions.