Ecosystem science and human–environment interactions in the Hawaiian archipelago
Tansley Lecture, delivered on 5 September 2005 at British Ecological Society Annual Meeting, Hatfield University, UK.
Peter Vitousek (tel. +1 650 7251866; fax +1650 7251856; e-mail email@example.com).
- 1Tansley's ecosystem concept remains a vital framework for ecological research in part because the approach facilitates interdisciplinary analyses of ecological systems.
- 2Features of the Hawaiian Islands – particularly the nearly orthogonal variation in many of the factors that control variation among ecosystems elsewhere – make the archipelago a useful model system for interdisciplinary research designed to understand fundamental controls on the state and dynamics of ecosystems, and their consequences for human societies.
- 3Analyses of rain forest sites arrayed on a substrate age gradient from c. 300 years to over 4 million years across the Hawaiian archipelago demonstrate that the sources of calcium and other essential cations shift from > 80% rock-derived in young sites to > 80% derived from marine aerosol on substrates older than 100 000 years. Rock-derived phosphorus is retained longer within ecosystems, but eventually long-distance transport of continental dust from Asia becomes the most important source of phosphorus.
- 4A biogeochemical feedback from low nutrient availability to efficient resource use by trees to slow decomposition and nutrient regeneration accentuates the geochemically driven pattern of low phosphorus availability and phosphorus limitation to net primary productivity in the oldest site.
- 5Variations in ecosystem biogeochemistry across the archipelago shaped the development and sustainability of Polynesian agricultural systems in the millennium between their discovery of Hawai’i and contact by Europeans. Irrigated pondfields were largely confined to stream valleys on the older islands, while rain-fed dryland systems occupied a narrow zone of fertile, well-watered soils on the younger islands.
- 6The ecosystem approach often represents the most appropriate level of organization for analyses of human influences on ecological systems; it can play a central role in the design and analysis of alternative agricultural, industrial and residential systems that could reduce the human footprint on the Earth.