A new study has found that the presence of moisture has a stronger role in developing areas of tropical vegetation than manmade CO2 emissions.
The research, undertaken by Dr William Gosling from the Institute for Biodiversity and Ecosystem Dynamics at the University of Amsterdam and supported by the OU, found previous suggestions that human-elevated CO2 could be mitigated by tropical plants or forests may be overestimating the vegetation’s need for CO2.
The research findings have large implications for developing effective climate mitigation strategies and are now published in Science.
At the Open University, Phil Holden, who performed the Earth system modelling in the study, said:
“Quantifying CO2 taken up by vegetation is essential if we are to know how much – and for how much longer – vegetation can assist the fight against climate change by mopping up some of our emissions. This study has given us new insight into which processes are most important in the tropics.”
Landscape scale
Previous research on individual plants, or forest patches, suggested that tropical vegetation could be a mitigating factor of CO2 levels: i.e. when more CO2 is released into the atmosphere, the vegetation will absorb more and thereby reduce the impact of this greenhouse gas.
The new study was scaled up to allow tropical vegetation change at a landscape scale and over timescales relevant to ecosystem change to be considered.
“We combined evidence of past environmental change extracted from Lake Bosumtwi in Ghana, with simulated past climate conditions, and the record of global atmospheric CO2 change obtained from ice cores over the last 500,000 years,” explains Gosling.
Moisture, fire and herbivory
This new research approach showed that atmospheric CO2 is less important than moisture availability, fire and consumption from animals (herbivory) in determining vegetation change.
Gosling added:
“Simply put, we have shown that it does not matter how much CO2 is in the atmosphere if there is not enough water, or there are fires every year, or all the seedlings are eaten by animals, you do not grow a forest.”
These research findings will have important implications for the global vegetation models and Earth system models that currently include a CO2 effect on the vegetation, but often do not include factors such as fire or herbivory.
Phil discussed the OU’s involvement:
“Aspects of this work go back to Will [Gosling] and I having adjacent offices at the OU back in 2010. We discovered a common interest in vegetation change across glacial cycles and wrote a paper that our modelled vegetation did not follow glacial cycles in the tropics.
“At that time Will was analysing the 500,000 year old lake core from Ghana with his PhD student Charlotte Miller at the OU. Since then work has been focused on developing approaches for data analysis and integration of datasets that allowed the strong link between changes in woody cover and moisture availability to be revealed.”
