Collapse and Restoration of Ecosystem Networks with Human Activity

Yamamura Norio RIHN

sakai Shoko RHIN 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 itioka 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 research on ecosystem degradation has focused only on its direct cause and effect in a particular place. This project applies new network sciences to the problem of ecosystem deterioration and collapse, and to the prospects of ecosystem restoration. The project examines social-environmental interactions in two distinct ecosystems where humans are dramatically altering ecosystems, and attempts to identify general properties of productive and destructive ecological change.

Objectives

Degradation of ecosystems, including loss of biodiversity and ecosystem functions, is widely viewed as a serious global environmental problem. To date, most research on the problem 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 society.

This project uses new network sciences to clarify the social and ecological patterns of exchange that lead to degradation of two endangered ecosystems in Asia. Recent advances in computer science and in theoretical studies on networks (i.e. complex system sciences, complex adaptive systems) have dramatically increased our ability to describe interactions between ecosystems and human societies. Complex system science can now lend important insights to the fields of sociology, economics, and ecology, and can offer richer description of the processes of ecological degradation and restoration.

Research sites

Field research takes place in tropical rainforests in Sarawak, Indonesia, and the grasslands of Mongolia (Photo 1). 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 demand from China. Though their ecological characteristics, such as the regeneration time of vegetation and position of humans in the food web, are quite different, the livelihoods of many inhabitants of these regions are dependent on natural ecosystems, and ecosystem destruction dramatically affects their practices and prospects.

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 increasingly available (photo by S. Sakai).

Research methods

The most important concept of this project is the “ecosystem network”; it describes a nested series of interactions among and within subsystems, including human societies, as shown in Figure 1. In both Sarawak and the grasslands of Mongolia, we are conducting research in three core steps: (1) identification of area-specific problems and the possible ecosystem network structures that can be related with them; (2) use of field survey, remote sensing and literature surveys to hypothesize and evaluate network links; and (3) scenario analysis of constructed networks, in which ecosystem and social outcomes are evaluated according to several indices. In integrating these results, we use the concept of ecosystem networks to establish a general theory of conservation. The core of the theory will indicate which network structures are likely to lead to environmental problems and how they can be mitigated.

Progress to date

In Mongolia, we: (1) found the most serious environmental problem to be increased degradation of pastures, especially near Ulan Bator, caused by overgrazing by an increasing number of livestock, especially goats (Photo 1A); (2) studied the social patterns leading to concentrations of livestock to urban areas; (3) analyzed climate data in order to clarify the roles of forests and shrubs in maintaining sustainable pastures (Fig. 2); and (4) conducted scenario analysis of the effects of several variables, such as improvement of transportation and protected areas, on pasture degradation.

In Sarawak, we: (1) found the most serious environmental issues to be the expansion of palm plantations and their negative effect on biodiversity and forest resources available to inhabitants; (Photo 1B); (2) conducted questionnaire surveys along the Rajang and Baram rivers, two main rivers in Sarawak, in order to identify the reasons (Fig. 3); (3) analyzed the effectiveness of, and problems with, institutions and systems such as forest certification and bioprospecting in regulating rapid plantation developments.

Finally, on the basis of the Mongolia and Sarawak case studies, we have begun to develop a general theory of conservation of ecosystem networks. In this process we have identified two important network effects: ripple effects that spread through the spatial structure, and positive feedback interactions between ecosystems and human behaviors.

Future issues to be addressed

The scenario approach has become popular in recent years. Well-known examples include those proposed by the Intergovernmental Panel on Climate Change (IPCC) to describe the significance of different levels of CO2 emissions, and those of the Millennium Ecosystem Assessment. In both cases, the scenarios assume a set of conditions according to a particular story line. We will use a similar approach. In the next two years, we will identify several plausible scenarios and evaluate them with several indices. Three provisional scenarios are: (1) business as usual; (2) infrastructure investment and development; and (3) changes in institutions.