GCTE

The Global Change and Terrestrial Ecosystems (GCTE) Core Project of the IGBP has much existing or planned research of relevance for the Mediterranean region and for Africa. The two overall objectives of GCTE are: to predict the effects of changes in climate, atmospheric composition, and land use on terrestrial ecosystems, including agricultural, forestry, soils and ecological complexity ; to determine how these effects lead to feedbacks to the atmosphere and the physical climate system.

The GCTE Core Research programme is organised around four major themes, or Foci: Ecosystem Physiology ; Change in Ecosystem Structure ; Global Change Impact on Agriculture, Forestry and Soils ; Global Change and Ecological Complexity.

Much of GCTE's international research effort is organised around networks and consortia, comprised of contributing research projects from countries and regions around the world. At present, about 700 research staff from 48 countries are involved in GCTE Core research. Many countries from the Mediterranean and Africa are contributing to GCTE networks and consortia.
In addition to these general contributions, there are four areas where Mediterranean and African scientists are making an especially important contribution to GCTE:

IGBP Terrestrial Transects. These large-scale transects are becoming a major research facility within IGBP. They are comprised of a set of integrated global change studies consisting of distributed observational studies and manipulative experiments coupled with modelling and synthesis activities organised along existing gradients of underlying global change parameters, such as temperature, precipitation and land use. The transects are designed to enhance collaboration among several IGBP core projects studying various aspects of global change related to terrestrial ecosystems (e.g., hydrology - BAHC, trace gas emissions - IGAC, and ecology - GCTE), and are proving particularly valuable as a tool for extrapolating the results of fine-scale process studies to the landscape, regional and global levels.

Perhaps the most advanced of the global set of transects is the SAvannas in the Long Term (SALT) transect in West Africa. This French-led effort is based on an integrated approach to studying processes linking the mechanisms of energy and mass flows to those of species and vegetation dynamics. SALT also focuses on analysing functional and dynamic processes at different spatial and temporal scales, i.e. understanding the ecological mechanisms driving changes in system properties, at increasing spatial scales from patch to region. Within SALT, studies are carried out at eight major sites and on a number of secondary sites stretching from Côte d'Ivoire to Niger.

A companion study based on the savannas of southern Africa, the Kalahari Transect, is now becoming operational. A feature of this transect study is an elevated CO2 experiment on a model savanna ecosystem, being carried out at the CSIR laboratories in Pretoria, South Africa. Two transects based on conceptual gradients of land-use change intensity are planned for Africa. One, in the dry tropical miombo woodlands, is in the advanced planning stages, while the other, to be based in the humid tropical forests of central Africa, is in the early planning phase.

Landscape Dynamics. GCTE is placing strong emphasis on understanding landscape-scale processes, such as disturbance (e.g., fire) and migration, both for their importance in constructing realistic global vegetation models and for studying global change impacts on terrestrial ecosystems. An early focus within GCTE landscape research will be on developing robust fire models, valid for a variety of ecosystems and under changing conditions of climate and land use. The Mediterranean region has traditionally been strong in research in landscape ecology, and will undoubtedly make a strong contribution to this area of GCTE. A workshop held in Toledo, Spain, in late 1993 launched GCTE's work on landscape dynamics under global change (see MEDIAS Newsletter n 4).

Soil Erosion. Within GCTE's Focus 3, a network studying the effects of global change on wind and water erosion has been established and is planning a series of model comparisons and synthesis workshops. Soil erosion is a particularly important topic for the Mediterranean, where the interaction between human-driven land-use change and climatic change will be important in determining rates of soil erosion, and in Africa, where land-use change is a dominant driving force. These two regions have strong representation in the GCTE soil erosion network, which is led by Dr Christian Valentin of ORSTOM. Dr Valentin is working on the SALT transect in West Africa.

Ecological Complexity. GCTE'S Focus 4 on Global Change and ecological complexity is only now becoming operational, but it is expected that a significant amount of research will be carried out on Mediterranean ecosystems, which have a comparatively high degree of biodiversity. GCTE's emphasis in Focus 4 is on the relationship between ecological complexity and ecosystem functioning, and the impact of global change on this relationship.