MONITORING OF ECOSYSTEMS USING REMOTE SENSING TECHNIQUES

1.Introduction

Mexico is one of 12 megadiverse countries in the world, accounting for between 60% and 70% of the total biodiversity worldwide (Mittermeir and Goettsch, 1997). Thus, the neccessity to achieve a sustainable development of our biological resources makes it important to know the spatial distribution of the vegetation, as well as its phenologic and anthropogenic modifications.

The aim of the "Monitoring of Ecosystems"-Program consists of the analysis of the detected changes -both in quality and quantity- and in the analysis of the distribution of vegetation through an enhanced methodology using remote sensing techniques, computing and statistics.

The existing biodiversity databank of CONABIO which describes the different species and their ecosystems will be employed in this study.

2.Objectives

a. To monitor the spatial and temporal distribution of the vegetation of Mexico in order to determine its annual and seasonal behavior and thus, to detect changes for a better understanding of phenological variations of the vegetation in Mexico throughout the seasons;

b. To design a specific methodology to identify vegetation types through large-scale satellite images, which may be applicable on different seasons and for many years; and

c. To estimate change rates from multitemporal analysis.

3.Research status in the international community

Within the international community, various projects on change detection have been carried out using remote sensing methods with images from different sensors; some of them are:

VEGETATION Program carried out by France, Belgium, Italy, Sweden and the European Commission using data from the new sensor VEGETATION of the SPOT-4 satellite, worldwide coverage (Initial Stage 1998). This sensor works with a 2200 km field of view and a resolution of 1.15 km (E. Bartholomé (CCR/SAI), 1997; in Internet: http://www-project.cst.cnes.fr:8050/)

TREES-Project: There is a global coverage project of the European Union with the purpose of obtaining information about changes in tropical vegetation using data from ERS-1/2 and NOAA-AVHRR; this study has a thematic resolution of five classes. This project has processed data available at a continental level. (MTV-Unit, JOINT RESEARCH CENTRE, TREES PROJECT) (Mayaux et al. 1997; Malingreau & Belward 1994).

NASA Pathfinder GAC Project by NASA (U.S.A), aimed at processing all GAC data available. The purpose of this project is to achieve global coverage of forest regions (Skole & Tucker 1993).

International Geosphere Biosphere Programme Data and Information System (IGBP 1990) (Townshend 1992).

In 1997, the Institute of Geography of the National Autonomous University of Mexico and the National Commission for Knowledge and Use of Biodiversity (CONABIO) carried out the project "Extraction of vegetation maps from high resolution AVHRR images," with the main purpose of making annual and seasonal vegetation maps for 1996. (Project J117 of Conabio).

In 1998, the National Commission for Knowledge and Use of Biodiversity (CONABIO) monitored fires with their corresponding biological "affectability." See the www page in this site: Monitoring of hot spots. During 1999 and 2000, the Institute of Geography of the National Autonomous University of Mexico and the National Commission for Knowledge and Use of Biodiversity (CONABIO) will carry out the project "Multitemporal analysis of vegetation conditions in Mexico through high resolution AVHRR satellite imagery." (Project T0114 of Conabio).

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