Alwyn Gentry was a field botanist of prodigious achievement, a prolific writer, energetic teacher and leader in the struggle to understand and conserve the world's remaining tropical forests - especially those in South America. His death, in a plane crash in Ecuador, at the age of 48, is a serious blow to tropical botany and conservation.
Gentry's research career spanned only 25 years, yet in this time his output and influence was more than most could manage in a lifetime's work. Beginning with a brief paper entitled 'A comparison of some leaf characteristics of tropical dry forest and tropical wet forest in Costa Rica' and culminating this year with the monumental 900-page Field Guide to the Families and Genera of Woody Plants of Northwest South America, his publications number almost 200, filling 6,000 pages of biological journals and books. A dozen of his works are the process of publication, and an enormous amount of his field data remain to be analysed. Undoubtedly, an equivalent amount of unpublished knowledge died with him.
Plant taxonomy is an intensive discipline, its practitioners absorbed in the detailed and careful analysis and description of the similarities and differences between plant species (often preserved as a single dried pressed specimen) and establishing their relationships. The scale of the task is such that a taxonomist can spend an entire career on a single plant family - or, in the case of some of the larger families like the legumes or orchids, just a section of the family.
Gentry was such a specialist: about a third of his publications concern the tropical Bignoniaceae, a family of often spectacular trees, shrubs and vines on which Gentry was the undoubted world expert; he described six new species from Amazonia only last year. But he was also a generalist, who mixed his detailed taxonomic studies with investigations of evolutionary ecology and vegetation patterns in the tropics; his work in the 1970s on the pollination biology of Bignoniaceae in tropical America provided important insights into how differences between species might be maintained.
In the last decade taxonomy has gained momentum and increasing attention, as a result of two factors: the development of molecular methods that add to (but are not a substitute for) the armoury of diagnostic techniques for classification, and the deepening crisis of biodiversity loss - which is especially acute in the tropics. As a field biologist, Gentry gained much of the impulse for his work from the latter. Although he worked throughout the tropics, most of his effort was concentrated in the Andean countries of South America, most notably Colombia and Ecuador, which harbour some of the highest concentrations of plant species (many yet to be adequately described) and are suffering some of the most rapid deforestation. His field trips not only established him as the most knowledgeable botanist for the region, but also encouraged an impressive flow of funds to biodiversity studies in the tropical regions of the New World and elsewhere.
Gentry collected more than 70,000 plant specimens. This quantity has been surpassed by few in the history of botanical collecting, most notably Dr Julian Steyermark, who was actively collecting and classifying well into his retirement. Steyermark, like Gentry, spent his younger years as a researcher at the Missouri Botanical Garden and, like Gentry, concentrated most of his effort on the tropical American flora. Both men, at different stages, contributed enormously to building Missouri's reputation as one of the world's leading centres for taxonomic research. The two collaborated on a single publication, 'A revision of Dilodendron (Sapindaceae)', in 1987. Gentry's publications list, in which he is mostly listed as sole author belies the extent to which he collaborated with other researchers.
Gentry's energy as a field companion was exhilarating and sometimes exasperating. To follow him through the forest as he reeled off the names of plants and pointed out possible new species was a delight and an invaluable education for any student or colleague. To arrive at the first campsite on the evening of the first of 10 muddy soaking days in the forest, and to discover that Al had provisioned the expedition with nothing but sugar, rice and a bottle of yellow colouring, was something quite different, but equally memorable. Given his easy sense of humour, there was always the suspicion that acts like these weren't entirely absent-minded.
Gentry devoted much of his energy to encouraging and helping students from the United States, South America and elsewhere. He was a good correspondent. His advice, always frank, ranged from the strictly botanical - 'If you know what your plants look like in your head, you can probably leaf through our Panama reference herbarium . . . and decide whether you can match your things or not' - to the minute practicalities of tropical field equipment - 'Although you could use almost any kind of mosquito netting, or even make a cloth box yourself, I used muslin, which has the advantage of keeping out insects and keeping one warm on cold tropical mornings . . . it has the disadvantage that it gets heavy when it gets wet.' His unfussy eagerness to communicate his knowledge is probably best exemplified by the above-mentioned Field Guide, which provides the most comprehensive and user- friendly introduction to the tropical South American flora yet published. He spoke (and wrote) good Spanish, with an uncompromising Midwestern accent.
Latterly, Gentry's work focused increasingly on biodiversity inventories - involving the rapid quantification and identification of the species present in sensitive and threatened tropical habitats. To be of value both for basic research and for establishing priorities for conservation, such research depends on an immensely detailed and reliable knowledge of flora and fauna. Like the ornithologist Theodore Parker, who died with him in Ecuador, Gentry was uniquely qualified to carry out this work. The tropical forests need more like him: he knew his plants like no one else.