Abstract—Ecotoxicology has focused

Abstract—Ecotoxicology has focused almost exclusively on countries and ecosystems in temperate zones. Tropical ecosystems, which combined contain as much as 75% of the global biodiversity, have been neglected. Tropical ecosystems are under increasing threat of development and habitat degradation from population growth and urbanization, agricultural expansion, deforestation, and mining. Some of these activities also lead to the release of toxic substances into the environment. Little research in ecotoxicology has been carried out in tropical environments. Techniques and procedures developed for temperate environments are often applied, even though physical and chemical environmental parameters in the tropics can be very different. Most research has focused on water quality and aquatic toxicology. The regulatory environment also varies among countries. We present a review of the literature on tropical ecotoxicology, with an emphasis on Latin America and the Caribbean. We also address priority areas for immediate research in the tropics. These include large-scale agricultural activities, especially banana, pineapple, and soybean farming, and gold mining with the associated heavy use of mercury. We outline the special issues that must be addressed as the field of tropical ecotoxicology progresses.

Keywords—Tropical ecotoxicology Rain forest Pesticides Neotropical migrants Biodiversity




INTRODUCTION

Tropical terrestrial and freshwater ecosystems cover only
25.7% of the land area on the surface of the Earth [1], but this area generates nearly 60% of the primary productivity of the planet [1] and contains approx. two-thirds of all the known species of vascular plants [2]. The number of species of most major taxa increases with decreasing latitude [3] (Table 1); thus, tropical ecosystems harbor the bulk of the world’s spe- cies. Some estimate that more than two-thirds of the world’s flora and fauna is found in the tropics [4].
Concern over the amount of environmental degradation in tropical ecosystems has increased dramatically over the past decade. The 1992 Earth Summit in Rio de Janeiro, Brazil, further catalyzed interest in the tropics, and the 1994
Summit of the Americas in Miami, Florida, USA, addressed hemispheric concerns over environmental problems in nations with tropical environments. A document prepared for the Miami summit presented examples of innovative approaches to sustainable development and conser vation in the tropics [5].
Innovative approaches are indeed necessary because tropical ecosystems are disappearing at an alarming rate (Table 2). Average annual deforestation between 1981 and 1985 in the Amazon Basin alone totaled 32,500 km2 year, an area equiv- alent to the U.S. states of Massachusetts and Connecticut com- bined [6]. Moreover, the annual deforestation rates of the coun- tries of the Amazon Basin (Table 2) are far less than those observed in other nations such as Thailand (2.7.%), Costa Rica (4.0%), and Nigeria (5.0%) [7].
Although deforestation is the most direct threat to tropical biodiversity, tropical ecosystems are currently threatened by

* To whom correspondence may be addressed. The current address of Thomas Lacher is Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843–2258, USA.

other human activities as well. Little research has been done on the impact of contaminants on tropical ecosystems, yet, considering research conducted in temperate regions, these compounds have potentially large effects [8]. In addition, trop- ical ecosystems are more poorly studied than temperate eco- systems, and the physical and chemical variables that affect biotic processes are different. We present an introduction to tropical ecosystems with a brief review of important environ- mental impacts and contaminant issues. We close this report with recommendations for applying the principles of environ- mental toxicology to the different ecological, sociological, and economic situations that are encountered in developing tropical countries.

The extent and nature of the tropics
Tropical environments differ ecologically from temperate zone habitats in physical, chemical, and biological attributes. Tropical environments occur between approx. 258 north and
258 south of the equator and are characterized by warm tem- peratures with little or no seasonality and heavy precipitation during at least part of the year [9] (Fig. 1). The tropics can be broadly classified into six major habitat types: tropical rain forests, tropical dry forests, tropical savannas, tropical wet- lands, tropical freshwater systems, and tropical marine envi- ronments [10] (Table 3).
Throughout the tropics, combinations of temperature and precipitation are encountered that do not exist in temperate regions. Our understanding of the fate and transport of envi- ronmental contaminants in northern latitudes has little appli- cability in the tropics [11]. In addition, biological diversity in the tropics is substantially higher than in temperate zones, and the number of species potentially affected by any given com- pound is also greater. Many taxa are poorly known, so little or nothing has been published on even the most fundamental aspects of their biology. New species are continually being


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