Alternatives to Slash-and-Burn 345and São Paulo–Rio Branco in Brazil, the Carretera Marginal de la Selva and the
Federico Basadre in Peru, and the Trans-Sumatra and Trans-Gabon highways have
provided access to forests to both small-scale farmers and commercial interests.
Many of these migrants are unfamiliar with the humid tropics, are largely
unaware of the knowledge-intensive practices of indigenous shifting cultivators,
and attempt to establish cropping systems that work where they came from (Moran,
1981). People in these situations usually lack alternative employment opportuni-
ties; have limited access to markets, credit and information; and often are politi-
cally marginalized. These people are a major focus of the ASB consortium.
The ASB Consortium
The ASB consortium is an international group of researchers, extension workers
and non-government organizations (NGOs) established in February 1992 to
investigate the causes and consequences of deforestation by small-scale farmers and
to identify land-use systems that enhance local livelihoods and the environment
and the policies and other changes needed to support them. The ASB focuses on
areas with high rates of deforestation where rapid increases in population density
caused primarily by inmigration result in conversion of natural forests and where
the environment–livelihood trade-offs are large. The ASB does not focus on shift-
ing cultivation, but in some locations where it did occur, it was included in the
comparative analysis. Similarly, larger-scale slash-and-burn operations also were
included in some of the comparisons.
State of knowledge
A literature review undertaken in 1992 showed much process-based understand-
ing of agricultural practices, empirical understanding of global environmental
processes and social processes, some policy research, and almost no multidiscipli-
nary research (Sanchez and Bandy, 1992; Bandy et al, 1993; Sanchez and Hailu,
1996). The biophysical processes of shifting cultivation and slash-and-burn sys-
tems have been well understood through decades of long-term, place-based research
(Nye and Greenland, 1960; Jurion and Henry, 1969; Sanchez, 1976; Juo and Lal,
1977; Seubert et al, 1977; Serrão et al, 1979; Macintosh et al, 1981; Toky and
Ramakrishnan, 1981; Sanchez et al, 1983, 1987; Ramakrishnan, 1984, 1987;
Smyth and Bastos, 1984; Von Uexkull, 1984; Alegre and Cassel, 1986, 1996;
Sanchez and Benites, 1987; Wade et al, 1988; Kang et al, 1990; Cerri et al, 1991;
Palm and Sanchez, 1991; Smyth and Cassel, 1995; Juo and Manu, 1996; Palm
et al, 1996).
The environmental consequences of slash-and-burn and tropical deforestation
on greenhouse gas emissions have been modelled or estimated with limited data on
the rates of deforestation, the carbon stored in the forests and subsequent land-use