PABITRA Island Landscapes under Global Change

PABITRA, the Pacific-Asia Biodiversity Transect Network, contributes in its geographic design a “Tropical East-West Island Belt” to DIWPA’s “Longitudinal Green Belt” and “Blue Belt.” The latter two incorporate a North-South gradient from cool-temperate to humid tropical, while the East-West island gradient ranges from low indigenous influx combined with high endemism to high indigenous influx with proportionately reduced endemism. These gradient designs harbor information of great scientific interest. PABITRA’s objectives are similar to DIWPA’s: to promote biodiversity assessment for interactive ecology and management. In an island context this means research and management to sustain the four biological resource zones, the upland/inland forests, the agroecosystems, and the freshwater and coastal salt water ecosystems in a functional balance under the pressures of global change.

Patterns of change

Islands, by definition, are small land masses surrounded by ocean. Smallness of landmass also implies narrow limits in the capacity to sustain the vitality of island ecosystems, which are encompassed in the four biological resource zones. A major impact of human invasion has been and continues to be the destruction of indigenous island forests. Because of loss of forest, some islands have lost their capacity to sustain human populations. Banaba (in Micronesia) and Kaho`olawe (in Northern Polynesia) are cases in point. Retrenchment of upland/inland forest watershed cover beyond a certain limit has shown negative effects on freshwater flow dynamics and quality. Pohnpei Island is a case in point. Stream diversion has dried up irrigated taro terraces in Hawai`i, affecting indigenous agriculture negatively. Here, the ahupua`a system of indigenous mountain-to-ocean management was crushed as a cultural heritage. Conversion of traditional polyculture into industrial monoculture (such as sugarcane in Hawai`i) proved to be unsustainable. Excessive use of fertilizer and pesticides for industrial agriculture has caused pollution and negative effects in coastal saltwater habitats. A chain reaction of negative effects from mountain to ocean can easily result from overexploitation of the vertically arranged ecosystems on island landscapes. Overexploitation in terms of habitat fragmentation with associated loss of native species and cultivars, invasion of unwanted alien species, and habitat conversion to unsustainable uses, are the main patterns of change. They threaten the ecological integrity and resilience of island landscapes as human support system.

Driving forces of change and ecological impacts

With some notable exceptions, island landscapes used to be sustainable under indigenous management as long as the human population was in balance with the islands’ biological resources. With accelerated growth of the human population and technological development came various forces of change, which we now recognize as “Global Change.” Anthropogenic influences on the rise of CO2 and other greenhouse gases were the first documented realization, which led to the still actively pursued research area of global warming, climate variability, and climate change. With this, much attention is also focused on sea-level rise and coastal erosion, which should have a disproportionably strong impact on islands. With CO2 enhancement, plant growth and plant metabolism is concomitantly enhanced, and competitive changes among plants are to be expected. For example, vines whose carbon allocation programs favor climbing ability and leaf area expansion over stem diameter and root production may play a greater role in vegetation changes. This has been shown in El Nińo induced rain forest fires in Kalimantan, where dried up climbers formed ladders that transferred ground fires into crown fires. Biological invasion has become a major force of change. It is the result of breakage of the traditional isolation barriers of biota by the mobility of humans as transfer agents and nature’s capacity to interact by unleashing the distribution capacity of neobiota. This is a troublesome and difficult to control force of change, particular in islands. The rich biological heritage in islands is also a cultural, spiritual, and economic heritage. These related forms of heritage are under threat due to global change.

Landscape research and management in terms of biodiversity

A time-proven management and human support system in islands is the vertical landscape unit starting with the watershed from mountain top (or mountain range) to coastal habitats including coral reefs, lagoons, estuaries, and small off-shore islands. In the PABITRA network, these vertical landscape segments also serve as the basic unit for multi-disciplinary research. PABITRA research is coordinated through the Ecosystem Division in the Biodiversity Task Force of the Pacific Science Association (PSA). It thus has a broad expert resource base. As an addendum to the DIWPA guidebook on “Biodiversity Research Methods”, PABITRA now has a draft manual for “Biodiversity Assessment of Tropical Island Ecosystems”, which is based on this landscape concept.

PABITRA’s major objectives can be summarized as follows:

Expected outcomes anticipated are as follows:

Recent PABITRA activities and limitations

PABITRA activities in the past two years have been the establishment of mountain-to-ocean landscape transects with biodiversity sites in Fiji and Samoa. This activity was funded by APN (the Asia-Pacific Network for Global Change Research) and involved in each case an Initial Synthesis Meeting and a major follow-up Joint Analysis and Field Training Workshop with local scientists, graduate students, land managers, and a select group of overseas resource people, or experts. Follow-up activities in Fiji were done by the local Fijian PABITRA team with self-generated new funding under the PABITRA umbrella. The same follow-up process cannot be expected as yet in Samoa, since there is a virtual dearth of trained field researchers and funding. The immediate goals of PABITRA are therefore to strengthen capacity building in Samoa, and to continue the landscape transect establishment approach in other islands. The next target islands are the Cook Islands (Rarotonga) and Palau (or Belau).

Budget and time frame

Dieter Mueller-Dombois, PhD
Emeritus Professor of Botany and Ecology
Chair of PSA Ecosystem Division and PABITRA Coordinator
Botany Department
University of Hawai`i at Manoa
Honolulu, Hawai`i 96822, USA

February 1, 2004