Philippe Mayaux

Tropical forest cover change in the 1990s and options for future monitoring

Despite the importance of the worlds humid tropical forests, our knowledge concerning their rates of change remains limited. Two recent programmes (FAO 2000 Forest Resources Assessment and TREES II), exploiting the global imaging capabilities of Earth observing satellites, have recently been completed to provide information on the dynamics of tropical forest cover. The results from these independent studies show a high degree of conformity and provide a good understanding of trends at the pan-tropical level. In 1990 there were some 1150 million ha of tropical rain forest with the area of the humid tropics deforested annually estimated at 5.8 million ha (approximately twice the size of Belgium). A further 2.3 million ha of humid forest is apparently degraded annually through fragmentation, logging and/or fires. In the sub-humid and dry tropics, annual deforestation of tropical moist deciduous and tropical dry forests comes to 2.2 and 0.7 million ha, respectively. Southeast Asia is the region where forests are under the highest pressure with an annual change rate of −0.8 to −0.9%. The annual area deforested in Latin America is large, but the relative rate (−0.4 to −0.5%) is lower, owing to the vast area covered by the remaining Amazonian forests. The humid forests of Africa are being converted at a similar rate to those of Latin America (−0.4 to −0.5% per year). During this period, secondary forests have also been established, through re-growth on abandoned land and forest plantations, but with different ecological, biophysical and economic characteristics compared with primary forests. These trends are significant in all regions, but the extent of new forest cover has proven difficult to establish. These results, as well as the lack of more detailed knowledge, clearly demonstrate the need to improve sound scientific evidence to support policy. The two projects provide useful guidance for future monitoring efforts in the context of multilateral environmental agreements and of international aid, trade and development partnerships. Methodologically, the use of high-resolution remote sensing in representative samples has been shown to be cost-effective. Close collaboration between tropical institutions and inter-governmental organizations proved to be a fruitful arrangement in the different projects. To properly assist decision-making, monitoring and assessments should primarily be addressed at the national level, which also corresponds to the ratification level of the multilateral environmental agreements. The Forest Resources Assessment 2000 deforestation statistics from countries are consistent with the satellite-based estimates in Asia and America, but are significantly different in Africa, highlighting the particular need for long-term capacity-building activities in this continent.

Determination of tropical deforestation rates and related carbon losses from 1990 to 2010

We estimate changes in forest cover (deforestation and forest regrowth) in the tropics for the two last decades (1990–2000 and 2000–2010) based on a sample of 4000 units of 10 ×10 km size. Forest cover is interpreted from satellite imagery at 30 × 30 m resolution. Forest cover changes are then combined with pan-tropical biomass maps to estimate carbon losses. We show that there was a gross loss of tropical forests of 8.0 million ha yr−1 in the 1990s and 7.6 million ha yr−1 in the 2000s (0.49% annual rate), with no statistically significant difference. Humid forests account for 64% of the total forest cover in 2010 and 54% of the net forest loss during second study decade. Losses of forest cover and Other Wooded Land (OWL) cover result in estimates of carbon losses which are similar for 1990s and 2000s at 887 MtC yr−1 (range: 646–1238) and 880 MtC yr−1 (range: 602–1237) respectively, with humid regions contributing two-thirds. The estimates of forest area changes have small statistical standard errors due to large sample size. We also reduce uncertainties of previous estimates of carbon losses and removals. Our estimates of forest area change are significantly lower as compared to national survey data. We reconcile recent low estimates of carbon emissions from tropical deforestation for early 2000s and show that carbon loss rates did not change between the two last decades. Carbon losses from deforestation represent circa 10% of Carbon emissions from fossil fuel combustion and cement production during the last decade (2000–2010). Our estimates of annual removals of carbon from forest regrowth at 115 MtC yr−1 (range: 61–168) and 97 MtC yr−1 (53–141) for the 1990s and 2000s respectively are five to fifteen times lower than earlier published estimates.

A joint initiative for harmonization and validation of land cover datasets

An international initiative aimed at the harmonization and validation of existing and future land cover datasets is needed to support operational earth observation of land. The goal is to overcome current limitations of land cover datasets with respect to their compatibility and comparability and unknown accuracy. These limitations significantly hinder a variety of applications. Key entities in this effort are the Land Cover Implementation Team of Global Observation of Forest Cover/Global Observation of Land Dynamics, the Global Land Cover Network, and the CEOS Group on Calibration and Validation. In their recent efforts, they have explored and provided the methodological and organizational resources to foster such an international cooperation. The approaches described in this paper include an introduction of the UN Land Cover Classification System as a common land cover language and a basis for legend translation. All actors involved in land cover mapping are invited to participate in this initiative

State and evolution of the African rainforests between 1990 and 2010.

This paper presents a map of Africas rainforests for 2005. Derived from moderate resolution imaging spectroradiometer data at a spatial resolution of 250 m and with an overall accuracy of 84%, this map provides new levels of spatial and thematic detail. The map is accompanied by measurements of deforestation between 1990, 2000 and 2010 for West Africa, Central Africa and Madagascar derived from a systematic sample of Landsat images—imagery from equivalent platforms is used to fill gaps in the Landsat record. Net deforestation is estimated at 0.28% yr−1 for the period 1990–2000 and 0.14% yr−1 for the period 2000–2010. West Africa and Madagascar exhibit a much higher deforestation rate than the Congo Basin, for example, three times higher for West Africa and nine times higher for Madagascar. Analysis of variance over the Congo Basin is then used to show that expanding agriculture and increasing fuelwood demands are key drivers of deforestation in the region, whereas well-controlled timber exploitation programmes have little or no direct influence on forest-cover reduction at present. Rural and urban population concentrations and fluxes are also identified as strong underlying causes of deforestation in this study.

The Forests of the Congo Basin: State of the Forest 2010

Meat from wild terrestrial or semi-terrestrial animals, termed „bushmeat‟, is a significant source of animal protein in Central African countries, and a crucial component of food security and livelihoods in rural areas. Estimates of bushmeat consumption across the Congo Basin range between 1 million tonnes (Wilkie and Carpenter 1999) and 5 million tonnes (Fa et al. 2003) and harvest rates are estimated to range from 23 to 897 kg/km 2 /year (Nasi et al. 2008). Many sustainability assessments focusing on tropical forest wildlife in the region have warned about the increasing unsustainability of hunting and associated ecological impacts (e.g. examples within Bennett and Robinson, 2000).The term “value chain” is useful to understand the activities involved in bringing a product from the forest, through processing and production, to delivery to final consumers and ultimately disposal (Kaplinsky & morris, 2000). Value chain analysis is a conceptual framework for mapping and categorizing the economic, social and environmental processes. It helps to understand how and where enterprises and institutions are positioned in chains, and to identify opportunities and possible leverage points for upgrading. This analysis encompasses the organization, coordination, equity, power relationships, linkages and governance between organizations and actors. Photo 7.1: Kola nuts (Cola acuminata) for sale in a market in Kisangani, DRC

Global Tropical Forest Area Measurements Derived from Coarse Resolution Satellite Imagery: A Comparison with other Approaches.

Definition of appropriate tropical forest policies must be supported by better information about forest distribution. New information technologies make possible the development of advanced systems which can accurately report on tropical forest area issues. The European Commission TREES (Tropical Ecosystem Environment observation by Satellite) project has produced a consistent map of the humid tropical forest cover based on 1 km resolution satellite data. This base-line reference information can be further calibrated using a sample of high-resolution data, in order to produce accurate forest area estimates. There is good general agreement with other pantropical inventories (Food & Agriculture Organization of the United Nations Forest Resources Assessment 90, World Conservation Union Conservation Atlas of Tropical Forests, National Aeronautics & Space Administration [USA] Landsat Pathfinder) using different approaches (compilation of existing data, statistical sampling, exhaustive survey with satellite data). However, for some countries, large differences appear among the assessments. Discrepancies arising from this comparison are here analysed in terms of limitations associated with each approach and they are generally associated with differences in forest definition, data source and processing methodology. According to the different inventories, the total area of closed tropical forest is estimated at 1090–1220 million hectares with the following continental distribution: 185–215 million hectares in Africa, 235–275 million hectares in Asia, and 670–730 million hectares in Latin America. A proposal for improving the current state of forest statistics by combining the contribution of the various methods under review is made.

National forest cover change in Congo Basin: deforestation, reforestation, degradation and regeneration for the years 1990, 2000 and 2005

This research refers to an object-based automatic method combined with a national expert validation to produce regional and national forest cover change statistics over Congo Basin. A total of 547 sampling sites systematically distributed over the whole humid forest domain are required to cover the six Central African countries containing tropical moist forest. High resolution imagery is used to accurately estimate not only deforestation and reforestation but also degradation and regeneration. The overall method consists of four steps: (i) image automatic preprocessing and preinterpretation, (ii) interpretation by national expert, (iii) statistic computation and (iv) accuracy assessment. The annual rate of net deforestation in Congo Basin is estimated to 0.09% between 1990 and 2000 and of net degradation to 0.05%. Between 2000 and 2005, this unique exercise estimates annual net deforestation to 0.17% and annual net degradation to 0.09%. An accuracy assessment reveals that 92.7% of tree cover (TC) classes agree with independent expert interpretation. In the discussion, we underline the direct causes and the drivers of deforestation. Population density, small-scale agriculture, fuelwood collection and forests accessibility are closely linked to deforestation, whereas timber extraction has no major impact on the reduction in the canopy cover. The analysis also shows the efficiency of protected areas to reduce deforestation. These results are expected to contribute to the discussion on the reduction in CO2 emissions from deforestation and forest degradation (REDD+) and serve as reference for the period.

African rainforests: past, present and future.

The rainforests are the great green heart of Africa, and present a unique combination of ecological, climatic and human interactions. In this synthesis paper, we review the past and present state processes of change in African rainforests, and explore the challenges and opportunities for maintaining a viable future for these biomes. We draw in particular on the insights and new analyses emerging from the Theme Issue on ‘African rainforests: past, present and future’ of Philosophical Transactions of the Royal Society B. A combination of features characterize the African rainforest biome, including a history of climate variation; forest expansion and retreat; a long history of human interaction with the biome; a relatively low plant species diversity but large tree biomass; a historically exceptionally high animal biomass that is now being severely hunted down; the dominance of selective logging; small-scale farming and bushmeat hunting as the major forms of direct human pressure; and, in Central Africa, the particular context of mineral- and oil-driven economies that have resulted in unusually low rates of deforestation and agricultural activity. We conclude by discussing how this combination of factors influences the prospects for African forests in the twenty-first century.

Estimating Tropical Deforestation from Earth Observation Data

This article covers the very recent developments undertaken for estimating tropical deforestation from Earth observation data. For the United Nations Framework Convention on Climate Change process it is important to tackle the technical issues surrounding the ability to produce accurate and consistent estimates of GHG emissions from deforestation in developing countries. Remotely-sensed data are crucial to such efforts. Recent developments in regional to global monitoring of tropical forests from Earth observation can contribute to reducing the uncertainties in estimates of carbon emissions from deforestation. Data sources at approximately 30 m × 30 m spatial resolution already exist to determine reference historical rates of change from the early 1990s. Key requirements for implementing future monitoring programs, both at regional and pan-tropical regional scales, include international commitment of resources to ensure regular (at least yearly) pan-tropical coverage by satellite remote sensing imagery at a sufficient level of detail; access to such data at low-cost; and consensus protocols for satellite imagery analysis.

Delivering a global, terrestrial, biodiversity observation system through remote sensing.

Land-cover change is of major concern to conservationists because of its generally negative impact on biodiversity (Brooks et al. 2002). There is a clear need to track these changes, and such information could make a major contribution to a global biodiversity observation system. Monitoring of biodiversity is an essential component of conservation because it allows problems to be identified, priorities to be set, solutions to be developed, and resources to be targeted (Balmford et al. 2003). Monitoring also allows assessments of progress toward targets and indicators in unilateral and international conservation-policy instruments (e.g., Convention on Biological Diversity [CDB]), of the impacts of international conservation policy (Donald et al. 2007), and of other policy sectors (Donald et al. 2001). Nevertheless, a paucity of information has led to a poor understanding of the cost-effectiveness of conservation policies (Ferraro & Pattanayak 2006), exposing them to criticism (Stokstad 2005). The overwhelming majority of species and ecosystems receive no systematic monitoring, and there is a conspicuous mismatch between the distribution of monitoring effort and the distribution of terrestrial biodiversity at a global scale (Green et al. 2005). The need to improve monitoring is widely recognized (Balmford et al. 2003; Pereira and Cooper 2006), and although some systematic monitoring of terrestrial biodiversity for conservation is undertaken locally in the developing world (e.g., Danielsen et al. 2008), there is no protocol to tackle the issue at a global scale. Traditionally, monitoring of popu-