SECO: Resolving the current and future carbon dynamics of the dry tropics

The ecosystems of the dry tropics are in flux: the savannas, woodlands and dry forests that together cover a greater area of the globe than rainforests are both a source of carbon emissions due to deforestation and forest degradation, and also a sink due to the enhanced growth of trees. However, both of these processes are poorly understood, in terms of their magnitude and causes, and the net carbon balance and its future remain unclear. This gap in knowledge arises because we do not have a systematic network of observations of vegetation change in the dry tropics, and thus have not, until now, been able to use observations of how things are changing to understand the processes involved and to test key theories.

Satellite remote sensing, combined with ground measurements, offers the ideal way to overcome these challenges, as it can provide regular, consistent monitoring at relatively low cost. However, most ecosystems in the dry tropics, especially savannas, comprise a mixture of grass and trees, and many optical remote sensing approaches (akin to enhanced versions of the sensors on digital cameras) struggle to distinguish changes between the two. Long wavelength radar remote sensing avoids this problem as it is insensitive to the presence of leaves or grass, and also is not affected by clouds, smoke or the angle of the sun, all of which complicate optical remote sensing. Radar remote sensing is therefore ideal to monitor tree biomass in the dry tropics. We have successfully demonstrated that such data can be used to accurately map woody biomass change for all 5 million sq km of southern Africa.

In SECO we will create a network of over 600 field plots to understand how the vegetation of the dry tropics is changing. and complement this with radar remote sensing to quantify how the carbon cycle of the dry tropics has changed over the last 15 years. This will provide the first estimates of key carbon fluxes across all of the dry tropics, including the amount of...