SUBJECT: Island Biodiversity conservation: some research priorities
AUTHOR: Jorge Palmeirim, Dept. Biologia Animal/Centro de Biologia Ambiental, Faculdade de Ciencias, Universidade de Lisboa, Lisbon, Portugal

SUMMARY: The author discusses research priorities in terms of invasive species, the interface between native and matrix habitats, the implementation of action plans, and anthropogenic pressures.

KEYWORDS: Invasive species, native vegetation, action plans, conservation.

The single most important threat to island biodiversity are probably invasive species, because the simplified animal and plant communities of islands seem to facilitate their overwhelming expansion. The devastating impact of some invasives, such as the replacement of native communities by continuous stands of exotic plants, is obvious. However, many spread discretely and their impact, even if serious and irreversible, may not be noticed without research. This is often the case of introduced predators, prey, seed dispersers, seed predators, etc. which can radically alter the food chains and the composition of the communities. While eliminating all exotic species may be an unrealistic goal, it is consensual that many must be controlled if we are to preserve insular biodiversity. However, there is still a critical lack of knowledge on the mechanisms that allow the expansion of exotics and on how to control them.

On some islands (e.g. in Macaronesia) there are patches of highly valuable native vegetation. These are often small “island within islands” and their long term survival is dependent on the capacity to resist invasion by species originating in the matrix of altered habitats. However, are birds carrying seeds of exotic plants into the native patches? Are exotic plants and invertebrates out-competing natives along the edges of the patches? Knowledge about what is occurring along the interface between native and matrix habitats is critical to plan conservation.

Some threatened endemic taxa (or communities) can only be saved with the implementation of specific action plans. However, much of the knowledge required for the preparation of those plans is missing. This includes the detection of the factors that are responsible for the decline of the taxa and the identification of the limiting factors that constrain their recovery.

On many islands space is often a limiting factor for both nature and Man, so conciliation between economic activities that occupy land and conservation is particularly important. Not all types of forest, agriculture, and urbanization are equally likely to result in habitats that support native species. However, we know little about how to make these man-made habitats more suitable for the preservation of threatened taxa, or for the maximization of biodiversity.

Finally, it is worth pointing out that much of the inter- and intra-species diversity made possible by island isolation is still uncharted. Some of this diversity may be lost before we become aware that it existed.

Considering the island conservation issues raised above I believe that the following should become research priorities:

1. Impact of invasive species on native communities and taxa;
2. Mechanisms that allow the spread of invasive species and methods to control them;
3. Ecological dynamics at the interface between valuable native habitat patches and the surrounding matrix;
4. Knowledge required for the preparation of species action plans for endemic species and communities, particularly about their limiting factors;
5. Agriculture and Forestry schemes that sustain native species.