Collapse and Restoration of Ecosystem Networks with Human Activity

Yamamura Norio RIHN

sakai Shoko RIHN

ishii Reiichiro Frontier Research Center for Global Change fujita Noboru RIHN ichikawa Masahiro Graduate School of Agriculture, Kochi University kamimura Akira Tokyo University of Foreign Studies ichioka Takao Graduate School of Human and Environmental Studies, Kyoto University matsuoka Masayuki Graduate School of Agriculture, Kochi University hyodo Fujio Center for New Technology, Okayama University

Many ecosystems have been seriously degraded by human activities and are now in critical condition. Nevertheless, most ecological research on ecosystem degradation has primarily focused on its direct cause and effect in a particular place. This project applies new network science to the problem of ecosystem deterioration and collapse, and to the prospect of ecosystem restoration. The project examines social-environmental interactions in two distinct areas where humans are dramatically altering ecosystems, and attempts to identify general characteristics leading to productive and destructive ecological change.

Project background

Degradation of ecosystems, including loss of biodiversity and ecosystem functions, is widely viewed as a serious global environmental problem. To date, much research has focused on the direct causes and effects of ecological degradation in a particular place. Few studies have adopted network-based analytical frameworks capable of describing the indirect and cascade effects characteristic of human-driven ecosystem change. Still fewer studies incorporate a social science perspective on ecological networks, even though environmental problems occur as a consequence of interactions between nature and human societies.

The key concept of our project is the ecosystem network, a concept describing ecosystem change in relation to a linked set of subsystems comprised of interacting social and ecological phenomena. Two ecosystem networks are investigated: those describing forest ecosystems in Sarawak and pastures in Mongolia (Fig. 1). Land-cover degradation is associated with intensifying land-use in both networks. Project research involves diversified field surveys, remote sensing and examination of existing literature in order to identify the most significant components and interactions causing degradation in each network. These indices then allow description of several possible future scenarios. As a whole, the two area studies enable construction of a general theory of ecosystem conservation.

Research sites

Field research takes place in tropical rainforests in Sarawak, Malaysia, and the grasslands of Mongolia. Export of raw materials is central to both economies. In the last few decades, social and environmental conditions in both places were profoundly affected by resource extraction, which has recently intensified in relation to new global economic demand. The ecological characteristics of these two places, including regeneration time of vegetation and position of humans in the food web, are quite different, but both ecosystems are critical to local livelihoods. Ecosystem degradation therefore dramatically affects local practices and prospects.

Research progress to date

In Mongolia, pasture degradation, especially near Ulan Bator, is the most serious environmental problem; it is caused by overgrazing linked to increasing populations of livestock, especially goats (Photo 1A). We observed patterns of livestock movement in order to understand actual utilization of grasslands (Fig. 2) and documented the social factors leading to concentrations of livestock near urban areas, causing pasture degradation. We also analyzed climate data in order to describe how forests and shrubs affect pastures, and conducted scenario analysis of the effects of several possible policies affecting use of pasture, such as limiting the total number and movement of grazing livestock, on pasture degradation.

In Sarawak, expansion of palm plantation and its negative effect on biodiversity and forest resources available to local inhabitants, is the most serious environmental problem (Photo 1B). Research therefore entailed questionnaire surveys in communities located along the Rajang and Baram rivers, two of the main rivers in Sarawak, in order to identify the factors allowing plantation expansion in those areas. We also conducted surveys in order to describe the effect of plantation expansion on local biodiversity, and noted a decrease in biodiversity in areas of higher intensity human activity. Finally, we conducted scenario analysis of the effects of several contemporary endeavours, such as forest certification and bio-prospecting, in mitigating plantation development.

We have begun to develop a general theory of ecosystem network conservation based on the Mongolia and Sarawak case studies. We note remarkable difference in grassland and forest ecosystem networks (Fig. 3). In Mongolia, grassland vegetation itself has no direct value to humans: its value is realized in livestock that feed on the grasses. Global demand for livestock products, especially cashmere, therefore affects the behaviour of dispersed local inhabitants, leading to overuse of the vegetation and degradation of the grassland. In this case, an effective solution to grassland degradation should involve behaviour-change of land managers, but this change is clearly linked to their collective position within the cashmere commodity-chain. In Sarawak, economic value resides directly in the forest trees. There is great economic incentive in clearing forest, with clear negative impact on biodiversity and the amount of forest available to inhabitants. Effective solutions in this case should involve direct regulation of enterprises and governments, perhaps linked to greater recognition of the indirect economic value of forests.

Photo 1  Recent environmental problems in Mongolia and Sarawak

A. The number of livestock, especially goats, is increasing rapidly, leading to degradation of pastures (photo by A. Maekawa). B. The number of oil-palm plantations is increasing all around Sarawak, and palm oil products are readily available (photo by S. Sakai).

Future issues

We have identified several potential scenarios in each ecological network under study, and now attempt to describe key scenario features, including prevalence of biodiversity, economic status of inhabitants, and continuation of traditional cultural practices related to long-term forest utilization. Even with extensive background data, predicting ecosystem network change is a challenge, as networks are dynamic and complex in themselves and also susceptible to external forces. General theories of ecosystem change will be improved through continual comparative analysis.