Improving Productivity, Profitability and Sustainability of Degraded Grasslands Through Tree-Based Land Use Systems in the Philippines - Smallholder Tree Growing for Rural Development and Environmental Services - page 276

14.1 Introduction
Uplands are important geographical components of Philippine agriculture. Vast
areas of the uplands in the Philippines are covered with grassland vegetation mostly
dominated by Imperata cylindrica or cogon indicating low soil fertility and produc-
tivity level. Historically, these vast degraded uplands are the results of a land use
transformation from natural forest to grassland areas through shifting cultivation
and consequently into permanent agriculture due to increasing population pressures
in the uplands (Bandy et al. 1993; Garrity and Agustin 1995).
Traditionally, shifting cultivation is sustainable with interspaced long fallow
periods. When the fallow period shortens, soil fertility declines significantly.
Grasses invade areas with soils low in organic matter and prone to soil erosion. In
the Philippines, the environmental consequences of shifting cultivation in upland
areas are severe and widespread with soil erosion as the worst outcome (World
Bank 1989). Estimated total annual soil loss from the Philippines varied from 74.5
million tons (DENR 1992) to 80.6 million tons (Francisco 1994). Soil erosion is a
natural process, however, it is greatly accelerated by human activities.
The intensive cultivation of upland areas without adopting appropriate soil con-
servation practices produces high rates of soil loss and threatens the long-term sus-
tainable productivity of the upland resource base (Francisco 1998; Nelson and
Cramb 1998). This has serious implications for the economic welfare of a growing
upland population with few feasible livelihood alternatives. There is evidence to
claim that the future of low input shifting cultivation in the uplands is grim (Menz
and Grist 1998). Where smallholder farmers continue intensive cultivation without
applying new technologies or inputs, returns to labor will fall and most of these
upland farms will no longer be viable (Menz and Grist 1998; Nelson et al. 1998;
Magcale-Macandog et al. 1998a). The challenge therefore is to improve the produc-
tivity and profitability of degraded uplands by enhancing (and subsequently main-
taining) the environmental quality of this resource in order to achieve sustainable
livelihood among upland smallholders.
Tree-based farming systems are potential profitable alternatives for improving the
productivity and sustainability of marginal upland areas. Tree growing is recognized
to be effective in the control of Imperata and other grasses through shading (Menz
and Grist 1996; Gouyon 1992). It also provides additional public benefits in the form
of carbon fixation by sequestering atmospheric carbon through their growth process
(Nowak 1993). Tree growing is the only known practical way to remove large vol-
umes of greenhouse gases (GHGs), especially carbon dioxide (CO 2 ), from the
atmosphere (Trexler and Haugen 1995). CO 2 is the most abundant and important
GHG under human control (Moura-Costa 1996; Houghton 1996) and it is expected
to account for more than 50 percent of the radiative forcing of GHGs released from
human activity over the next century (Houghton 1996; Houghton et al. 1990).
In this study we aimed to quantify the economic and environmental impacts of
grassland conversion to tree-based land use systems. Specifically, we here (i) esti-
mate and analyze the private profitability, social and environmental benefits of