A living laboratory

There are now many books about the rainforest, but this one is refreshingly different because it is about a small reserve of only 1,536 hectares at the La Selva Biological Station in Costa Rica. The station, which belongs to the Organisation for Tropical Studies (OTS), facilitates tropical research and education by providing an accessible field site with well-equipped living and laboratory facilities.

Since OTS took over Fisca La Selva in 1968, it has trained and inspired many of today's tropical biologists. And many of La Selva's former pupils have contributed to this book.

Work conducted at La Selva has made one of the most significant contributions to tropical ecology and natural history this century. Much of the basic information about the ways in which rainforests work has come from La Selva and is brought together here in a well-constructed book that covers a wide range of topics. This is a report about real field-based observational research, rather than theoretical ecology which has tended to dominate the scene recently.

Much attention has been drawn to Costa Rica because of the range of biological habitats it offers, owing to the presence of mountains, lowlands with dry forest, tropical rainforest and many other types of vegetation. It is probably the most biodiverse country in the world for its size. While a large percentage of its territory has been designated conservation areas, it also has the highest rate of deforestation of any country in Latin America. By 2000, little natural rainforest will remain outside reserves, probably putting pressure on the integrity of the reserves.

La Selva is a small part of Costa Rica. It is a lowland area that does not have any of the interesting cloud forests of the mountains, yet it is an extremely diverse property. It contains more species of plants than the entire flora of the British Isles with 1,678 species of flowering plants and ferns, 1,458 of which are native. Four hundred and forty-one species of birds have been observed; there are more than 4,000 species of moths and 500 of butterflies. It is hardly surprising that this little patch of rainforest has become a living laboratory that is answering some of the vital questions about how rainforests work.

The success of La Selva is that it has been used by scientists of many different disciplines who have collaborated and exchanged ideas, and this book presents a good balance of the research.

The physical environment, such as the climate, the soils, the geomorphology, energy and nutrient cycles are described in the opening chapters. The diversity of plants and animals in the reserve and the ecological processes described all depend upon these physical factors.

After sections on plants and animals and the communities in which they live, a further section is devoted to a fascinating array of plant-animal interactions, which is where the research at La Selva has excelled. Here we read about ants that feed on extra floral nectarines and protect the plants from other predators and about intricate pollination and dispersal mechanisms.

Unlike the forests of Europe, where each species of tree occurs in great abundance, tree species in tropical rainforests are widely spread. Despite this, the work at La Selva has shown that most tree species are out-breeders that require pollen from another tree of the same species to set seed. A wonderful variety of precise mechanisms has evolved in rainforest to deliver pollen precisely from one tree to another, involving such animals as bats, hummingbirds, large bees that fly along precise daily routes from one flowering tree to another, butterflies and hawk moths.

The book finishes with a masterful overview that synthesises the information presented about species richness, habitat diversity and the ways in which different species have adapted and places a strong emphasis on the need for further comparative studies between La Selva and other parts of the tropics. It is good to end with a chapter that looks out from La Selva to the whole world of tropical rainforests and we need to heed the plea of Gordon Orians for more research that uses similar methodology so that work in different places can be truly comparative.

One of the most impressive aspects of this book on the most studied piece of rainforest in the world is that almost every author outlines the need for further research in his or her own area of expertise. For example, only one plant species, the fern Danaea wendlandii, has been examined demographically. Do not think that all the work has been done at La Selva; there is still plenty more to be done and each chapter makes helpful suggestions for future students of rainforest.

The fact we know so little about the processes that control the rainforest is tragic at a time when so much of it is being destroyed. It is the type of research being carried out at La Selva that will give the answers as to how to use rainforest sustainably, how to conserve it for future generations and simply how to enjoy the natural history of the diversity of plants it contains.

Ghillean T. Prance is director of the Royal Botanic Gardens, Kew.