It’s well known that the largest remaining tropical rainforest on Earth, that of the Amazon, is undergoing rapid deforestation.

The rate of clearing in the Brazilian Amazon is now one of the world’s highest, and may have even increased to 25,500 square kilometres between 2001 and 2002.

What’s less well appreciated is that the rate of deforestation of the Brazilian Amazon does not depend solely on forest policies, or on a particular piece of forest’s inaccessibility.

Currently 80% of the land cleared is not for timber, but to create cattle ranches. So to understand the causes of deforestation in the Brazilian Amazon, researchers need to understand the forces that influence how much land will be cleared for cattle ranching in different areas at different times.

Benoit Mertens from CIFOR, and colleagues (from CIRAD in France, and EMBRAPA, INPE and IPAM, in Brazil), used high-resolution satellite images and economic data to analyse some of the complex factors behind deforestation in Brazil’s Amazon.

Their fascinating findings, published in Agricultural Economics in December 2002 and Bois et forêt des Tropiques (in press), show a whole range of economic, social and developmental factors come into play.

Satellite images for the periods 1985-1992 and 1992-1999 showed intensive forest clearing in all study areas, with the rate of deforestation increasing in the 1990s. Most of the forest clearings were devoted to pasture, but the intensity and patterns of clearing were not uniform.

To understand why there are different rates of clearing, the team compared the history of clearing between several regions in the state of Pará (particularly São Félix do Xingú in Southern Pará) and the region of Uruará along the Transamazon Highway.

Since the middle of the 1980s, the dominant process of land use change in São Félix do Xingú has been the conversion of forest to pasture.

Between 1986 and 1999, 42% of forest loss was to small-scale ranchers in government colonization projects, while 23% came from medium-sized ranches and small ranchers outside colonization projects.

Smallholders in São Félix do Xingú have become integrated in livestock production and marketing chains. The calves are sold to the large ranches (fazendas) that fattened them for sale to the big factories. These smallholders also sell milk to modern dairy plants attracted to the area by public investment in electricity, roads, and credit.

During the same period, 35% of the land cleared was for large cattle ranches. New roads connected south Para with northeast and southeast Brazil, giving meat producers in south Pará access to major urban markets.

To supply those markets investors built large slaughterhouses and refrigerated meatpacking plants, which in turn bought increasing numbers of cattle from the fazendas.

“This seems to simulate both intensification of cattle production, particularly close the slaughterhouses and the main roads, and extensive production systems through new forest clearings” said Mertens.

But in the second study area of Uruará, the researchers found more complex land use trajectories.

The Uruará region is characterised by state-directed colonisation settlement program, and a high proportion of small-scale farmers. Such systems typically include annuals (such as rice and beans), perennials (cocoa, pepper and coffee) and pasture.

But the prices and yields of the main perennial crops fluctuate, and since the 1990s more smallholders are turning to livestock, which provides lower but safer returns.

However, small farmers in Uruará still do not rely exclusively on cattle for income, and demand is lower than is São Félix do Xingú.

Because of these factors, the rate of deforestation in Uruará was much lower in the period studied (and from a much lower base) - but still increasing over time.

Another interesting finding had to do with property rights. It is often claimed that many farmers clear land in order to gain property rights. Because of this, improving local land tenure policies is suggested as a tool to prevent deforestation.

But this study confirmed earlier findings from other researchers, that small landholders with secure land tenure clear forests at the same rate as those who do not.

“In Uruará, where most of the small holders have secure property right, deforestation has tended to increase over time. In São Félix do Xingú, farmers with secure land tenure seem to be protected from land concentration but do not deforest less,” Mertens said.

The issue is more complex for large-scale properties since some large landholders consider that forest clearing prevents them having their land expropriated or invaded by landless people.

With the rapid rate of change in these agricultural frontiers, this is one of many areas the researchers believe needs more work.

According to the authors of the report, both land use and regional development trajectories result from region-specific combination of factors and drivers of land use change. Any future scenarios of land use change in the Amazon should thus consider such sub-regional specificities.