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A great number of studies have been dealing with land-cover mapping of tropical regions using earth remote sensing technology recently. This is partly due to a growing number of operational sensor systems for both scientific and commercial use and also because of an increasing demand for land-cover information relevant to global environmental issues and international policy instruments (e.g. the Kyoto protocol). Within this context, the present article discusses the state of the art of data processing and analysis for the assessment of broad scale land-cover and land-cover change in tropical regions. Current global scale land-cover maps are compared with regional satellite mapping products (Landsat/ETM+) for a test region in the humid tropics of Central Sulawesi, Indonesia.

The paper suggests the land cover classification system (LCCS) to be used as the conceptual basis for future land-cover analysis in Sulawesi because it delivers a consistent and comparable scale-independent class structure for satellite image-based land-cover mapping and monitoring. The results of the comparative analysis of land-cover and land-cover change document the inhomogeneity, inconsistency and hence high uncertainty of existing estimates. The outcome of the harmonized and generalized land-cover products for two base years (1992 and 2000) indicates considerable disagreements in area estimates and spatial distributions of land-cover classes for a single date that in some cases exceed the detectable changes between years.

Future work aiming at a long-scale operational land-cover mapping of tropical environments has to account for (a) a further harmonization of existing and planned land-cover definitions and products, (b) the regional validation of products and (c) the implementation of a multi-level standardized technical and conceptual classification workflow for ecosystem mapping and monitoring in tropical regions.

Greenhouse gas and energy fluxes between the land surface and the atmosphere are important aspects for the evaluation of land-use options in tropical areas. Changes in vegetation cover alter the capacity to absorb carbon dioxide and solar radiation from the atmosphere and influence the magnitudes of latent and sensible heat flows to the atmosphere. If happening at a larger spatial scale, land-use change can lead to significant local feedbacks like drought, flooding, soil erosion or shifts in local climate.

Up to now only little was known about how typical ecosystems of the rain forest margin areas interact with the atmosphere. We present here results from a sub-program of STORMA (Stability of rain forest margins in Indonesia, SFB-552-B1), to describe the energy, CO and water fluxes between a larger tropical area and the atmosphere.

Field measurements with the eddy correlation method showed that a Cacao agroforestry system (AFS) was a small source of CO, whereas a tropical rain forest was a strong CO sink during the one year observation period. In addition, the rain forest evaporated much more water compared to the Cacao AFS.

We applied a series of models to extrapolate the results from the field investigations to the region, including so-called SVAT models of differing complexity, and a simple PAR efficiency model to predict net primary production from regional meteorological and remote sensing data. In all cases, we discovered a large spatial variability in CO and water vapour fluxes. We investigated the sensitivity of the models to changes in climatic drivers or land-use parameters from the current to a more intensified agriculture. The selected land-use scenarios reduced carbon dioxide sequestration and total evaporation and increased sensible heat fluxes and thus surface temperatures.

We conclude that there is still a lack of field observations to better understand and simulate the behaviour of tropical land-use systems. If the necessary detail on model parameter values, which characterise the differences between the land-use systems, is known, the existing model approaches are suitable to investigate consequences of land-use change to regional biogeochemical cycling, water utilisation and climate change.

Deforestation in the Brazilian Amazon increased from 10 million hectares in the 1970s to more than 60 million hectares at the turn of the century, resulting in growing awareness about deforestation impacts like greenhouse-gas emissions, loss of biodiversity, and motivating a number of initiatives involving the science and technology (S&T) field to address the issues of deforestation and sustainable development in the Amazon. The present work summarizes part of the large-scale land cover-use changes that occurred in the region and then analyses the organization of four S&T programs carried out in the Amazon in the context of alarming deforestation rates and rapidly changing land use in the Amazonian frontier. The four programs include two major research programs - the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA) and the Science & Technology Subprogram (S&T) of the Pilot Program to Conserve the Brazilian Rain Forest (PPG7) - and two examples of environmental monitoring and management - the Ecological-Economic Zoning (ZEE) and deforestation monitoring programs. In the context of high rates of forest loss and generally very weak institutions, the initiatives organized with the concourse of the S&T field may have significantly contributed to advance the discussions of sustainable development and sustainable land use in the frontier, and to mature some ideas about the participation of civil society, national environmental policy and, also, international cooperation. These exercises also suggest that the tasks of reducing and mitigating deforestation impacts and fostering sustainable land use are not to be engineered but, rather, negotiated, and that understanding how to contribute to such negotiations seems to be a major challenge for the science and technology field in Brazil.