FOREST AREA IN COSTA RICA: A COMPARATIVE STUDY OF TROPICAL FOREST COVER ESTIMATES OVER TIME CHRISTOPH KLEINN 1∗ , LENIN CORRALES 2 and DAVID MORALES 1 1 Statistics Subunit, Tropical Agricultural Research and Higher Education Center (CATIE), Turrialba, Costa Rica; 2 Freelance Consultant, San José, Costa Rica ( ∗ author for correspondence, e-mail: ckleinn@catie.ac.cr) (Received 14 February, 2000; accepted 10 November, 2000) Abstract. Forest area figures, at a given point in time and for a given region of interest, differ con- siderably, affecting the calculation of deforestation rates and thus confuse the political and scientific discussion on the state and change of the resource forest. This article discusses the variation of pub- lished forest cover figures, using Costa Rica as an example. A list of published figures on the forest cover of Costa Rica from 1940 onwards is analyzed. Reasons for the differences are hypothesized and discussed. These differences are mainly in the definition of forest and forest classes included, in the type of the studies conducted (mapping and/or sampling), in the precision of the estimates, and in the information sources used. It is concluded that part of the problem is inherent in the nature of the resource ‘forest’. Quality and completeness of the presentation of the forest cover estimates are a clue to their correct understanding and interpretation. The latter point being especially relevant, as forest cover data have both a technical-scientific and a political meaning and are used as relevant arguments in many discussions. In the example of Costa Rica, a general downward trend is observed up to about 1985/1990, whereas after that forest area figures are on the average at a markedly higher level. Some hypotheses for this change in the trend are discussed. Keywords: Costa Rica, forest definition, forest inventory, forest mapping, tropical deforestation 1. Introduction Large area data on state and change of the environment and of the natural resources has become a key issue of national and international environmental and develop- ment politics, as is reflected in a number of international conventions, agreements and protocols, particularly recognized through the United Nations Conference on Environment and Development (UNCED) in 1992 in Rio de Janeiro. Forest data play a particularly important role in many agreements like Agenda 21, the Forestry Principles, and the conventions on climate change, desertification and biological diversity (Lund and Boley, 1995). Forest cover is politically sensitive information. It is among the national-level indicators for the evaluation of sustainability, particularly when broken down into forest types, age classes and successional stages (Lammerts van Beuren and Blom, 1997), is easily understood and can supposedly easily be measured. However, pub- lished forest cover data often differ considerably making it a challenge to decide Environmental Monitoring and Assessment 73: 17–40, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.