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First six years of GCTE

The International Geosphere-Biosphere Programme (IGBP) has released a report on the major findings of the first six years of its Global Change and Terrestrial Ecosystems (GCTE) Core Project. We present extracts from the executive summary IGBP Science No. 1: A Synthesis of GCTE and Related Research.

The accelerating changes to the Earth’s environment are being driven by growth in the human population, by the increasing level of resource consumption by human societies and by changes in technology and socio-political organizations.

Four aspects of large-scale environmental perturbations are considered here under the term “global change.” They are:

  • (i) changes in land use and land cover;
  • (ii) the world-wide decline in biodiversity;
  • (iii) changes in atmospheric composition, especially the increase in CO2 concentration; and,
  • (iv) changes in climate.

From the perspective of terrestrial ecosystems, the most important component of global change over the next three or four decades will likely be land-use or -cover change. It is driven largely by the need to feed the expanding human population, expected to increase by almost one billion people per decade for the next three decades at least. Much of this increase will occur in developing countries in the low-latitude regions of the world. To meet the associated food demand, crop yields will need to increase, consistently, by over two per cent every year through this period.

Despite advances in technology, increasing food production must lead to intensification of agriculture in areas which are already cropped, and conversion of forests and grasslands into cropping systems. Much of the latter will occur in semi-arid regions and on lands which are marginally suitable for cultivation, increasing the risk of soil erosion, accelerated water use, and further land degradation.

The need to meet a two per cent per annum or greater increase in food demand will put enormous stresses on managed production systems. Climatic change will likely further stress these systems. Extreme weather events, such as back-to-back droughts in one, or simultaneous droughts in two or more, of the world’s major grain producing areas would create severe food shortages.

One response to the food supply issue is technology: the development of improved cropping systems and/or crop varieties. There is no doubt that improved varieties, such as genetically engineered crops with built-in insecticides and short season varieties with high water use efficiencies, will offset some of the increased demand. However, biotechnology has not yet succeeded in improving our capability to cope with complex system-level problems, such as drought and salinity.

A sustained increase in global production of the required two per cent a year may well be achieved, but it will have considerable impact on land use and on ecosystems in general. Climate change makes the task of producing the additional food and fibre more uncertain.

The availability of resources will continue to constrain agricultural development in many regions. For example, water availability, already a major problem, is likely to become increasingly limiting as agricultural, industrial and urban demands for water compete more directly with the need to maintain river flows for conservation and waste removal and purification purposes.

Global change is occurring now, will continue for the foreseeable future and is likely to intensify in many aspects. It is an emerging reality that will increasingly impact on the political process, on regional strategic planning and on the daily lives of resource managers. Learning to live with global change, to avoid the worst of the hazards and capitalize on opportunities as they arise, requires creative and innovative strategies. These must be built upon a sound scientific understanding of terrestrial ecosystem interactions with global change. Although GCTE and similar efforts have made good progress in the last six years, large challenges remain, both in the basic understanding of the science and in the development of research tools to improve that understanding.

How can, or should, society use current scientific understanding in responding to global change? An example of this difficulty is the current debate on the “take action now” vs. “take action later (or take no action)” proposals to limit greenhouse gas emissions. There are global processes which have lag times of decades or even centuries. The consequences of not taking action now may therefore not be felt until the middle of next century, but when these consequences do occur, they could be serious and very difficult to address. An example of such a lag effect is the diminishing ability of the terrestrial biosphere to absorb carbon as both atmospheric CO2 concentration and temperature increase; a lack of action now could lead to a large, unavoidable, additional CO2 release a century or so from now, through increasing decomposition of soil organic matter (about twice as much carbon is stored below-ground than above in terrestrial ecosystems).

The bottom line is that we will probably never be able to predict, with a high degree of certainty, precisely how terrestrial ecosystems will interact with accelerating environmental change. Thus, the analogy that ecosystems can be “managed” in the same way that much simpler human-designed industrial systems can is misleading and dangerous. In terms of terrestrial ecosystem interactions with global change, we must expect the unexpected (and unpredictable), and keep open as many response options as possible.

There is an inescapable trade-off between resilience and production in managed agroecosystems: the most productive systems are often the simplest, but they are the least resilient to disturbance and perturbation. Highly productive systems are required to feed an expanding population; complex, resilient systems are required to be able to respond to future shocks and disturbances, and to continue providing the ecosystem “goods and services” we need.

Learning to strike the right balance in this dichotomy is the biggest environmental challenge facing humanity in the 21st century.

Further information

The summary report, IGBP Science No. 1, is available free from the IGBP Secretariat. The full results of the review are available in the IGBP Book Series (No. 4) published by Cambridge University Press. For further information about GCTE, contact the GCTE International Project Office, CSIRO Division of Wildlife and Ecology, PO Box 84, Lyneham, ACT 2602, Australia. Fx: 61-2-62412362. Email:

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