Rates of change in terrestrial ecosystems

"Globally, the rate of conversion of ecosystems has begun to slow largely due to reductions in the rate of expansion of cultivated land, and in some regions (particularly in temperate zones) ecosystems are returning to conditions and species compositions similar to their pre-conversion states. Yet rates of ecosystem conversion remain high or are increasing for specific ecosystems and regions.

Under the aegis of the MA, the first systematic examination of the status and trends in terrestrial and coastal land cover was carried out using global and regional datasets. The pattern of deforestation, afforestation, and dryland degradation between 1980 and 2000 is shown in Figure 1.4. Opportunities for further expansion of cultivation are diminishing in many regions of the world as most of the land well-suited for intensive agriculture has been converted to cultivation. Increased agricultural productivity is also diminishing the need for agricultural expansion.

As a result of these two factors, a greater fraction of land in cultivated systems (areas with at least 30% of land cultivated) is actually being cultivated, the intensity of cultivation of land is increasing, fallow lengths are decreasing, and management practices are shifting from monocultures to polycultures. Since 1950, cropland areas have stabilized in North America and decreased in Europe and China. Cropland areas in the Former Soviet Union have decreased since 1960. Within temperate and boreal zones, forest cover increased by approximately 2.9 million hectares per year in the 1990s, of which approximately 40% was forest plantations. In some cases, rates of conversion of ecosystems have apparently slowed because most of the ecosystem has now been converted, as is the case with temperate broadleaf forests and Mediterranean forests