Understanding Tropical Deforestation with Remote Sensing and GIS Modeling

July 30, 2008 By: Samuel Rivera, R. Douglas Ramsey, Pablo MartinezdeAnguita, Hernandez , Alexander J

Deforestation rates in the tropics have reached alarming dimensions. Around 62 percent of the primary forest of tropical ecosystems has been already lost. It is estimated that during the 1990s, the global deforestation rate in the tropics reached 15.4 million hectares/year.

The rate of deforestation in Central America is even higher than South America (1.5 percent and 0.6 percent, respectively), where the giant Amazon jungle is located (World Bank, 2000). In Honduras, a hectare of forest is cleared for agriculture every five minutes (Rivera, 2004). The occupation of fertile and productive lands is forcing small farmers to migrate and cultivate on the steep hillsides.

The disruption of environmental equilibrium is reflected in problems affecting agriculture, water management, marine resources, wildlife, and human health. As a result, this phenomenon brings serious consequences to the environment, including loss of soil fertility, soil erosion, river channel sedimentation, reduction of hydroelectric-generated power, decreased habitat for wildlife, declining drinking water quality, increasing floods, etc. This vicious circle of poverty and environment deterioration is one of the primary causes of human migration to developed regions (World Bank, 2000).

Local government agencies are struggling to find ways to perpetuate and concentrate farmers' activities in one area, and reduce migration to forested areas to be cleared for agriculture. In order to implement this, substantial improvements of their technologies need to be applied, so they can improve production and productivity (Pascual, 2005). A solution to minimize erosion and deforestation rates is to stabilize farmers in one site and promote the implementation and adoption — over the long term — of conservation measures (Hellin and Schrader, 2003). Historically, farmers have not adopted these measures, primarily because of their lack of knowledge concerning the advantages of their use, and the lack of incentives to do so (Lutz et al., 1994).

Setting Up the Study

Remote sensing platforms and geospatial data offer a unique opportunity to study the impact of land-use changes as a dynamic process in time and space, and provide proactive solutions to river basin monitoring. Locations that require soil conservation or restoration measures can be identified through a GIS spatial model. A remotely sensed approach intended to represent current land use is able to account for the spatial variation present in the entire basin. Processed multi-temporal satellite imagery, coupled with the spatial analysis capabilities of GIS, can distinguish different land use changes, dynamically map how they vary in space, and provide insight into the effects of land-use change and erosion rates (Zancajo and Mostaza, 2004).