PILOT ANALYSIS OF GLOBAL ECOSYSTEMS

Ken Kassem; Norbert Henninger

PILOT ANALYSIS OF GLOBAL ECOSYSTEMS

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The Pilot Analysis of Global Ecosystems (PAGE) investigates the health and sustainability of the world's ecosystems, emphasizing the vital interdependence between human life and ecosystem health. It compiles a comprehensive assessment of five major ecosystem types—agroecosystems, coastal areas, forests, freshwater systems, and grasslands—highlighting the significant impact of human activities on their extent and condition. The findings suggest a decrease in the capacity of ecosystems to provide essential goods and services, demanding urgent changes in management practices and increased political commitment to ecosystem viability.

Copyright 2005 Millennium Ecosystem Assessment All rights reserved under International and Pan-American Copyright Conventions. No part of this book may be reproduced in any form or by any means without permission in writing from the publisher: Island Press, 1718 Connecticut Avenue, Suite 300, NW, Washington, DC 20009. ISLAND PRESS is a trademark of The Center for Resource Economics. Library of Congress Cataloging-in-Publication data. Ecosystems and human well-being : current state and trends : findings of the Condition and Trends Working Group / edited by Rashid Hassan, Robert Scholes, Neville Ash. The Millennium Ecosystem Assessment was carried out between 2001 and 2005 to assess the consequences of ecosystem change for human well-being and to establish the scientific basis for actions needed to enhance the conservation and sustainable use of ecosystems and their contributions to human well-being. The MA responds to government requests for information received through four international conventions—the Convention on Biological Diversity, the United Nations Convention to Combat Desertification, the Ramsar Convention on Wetlands, and the Convention on Migratory Species—and is designed to also meet needs of other stakeholders, including the business community, the health sector, nongovernmental organizations, and indigenous peoples. The sub-global assessments also aimed to meet the needs of users in the regions where they were undertaken. The assessment focuses on the linkages between ecosystems and human well-being and, in particular, on ‘‘ecosystem services.’’ An ecosystem is a dynamic complex of plant, animal, and microorganism communities and the nonliving environment interacting as a functional unit. The MA deals with the full range of ecosystems—from those relatively undisturbed, such as natural forests, to landscapes with mixed patterns of human use and to ecosystems intensively managed and modified by humans, such as agricultural land and urban areas. Ecosystem services are the benefits people obtain from ecosystems. These include provisioning services such as food, water, timber, and fiber; regulating services that affect climate, floods, disease, wastes, and water quality; cultural services that provide recreational, aesthetic, and spiritual benefits; and supporting services such as soil formation, photosynthesis, and nutrient cycling. The human species, while buffered against environmental changes by culture and technology, is fundamentally dependent on the flow of ecosystem services.

Analytical Approaches for Assessing Ecosystem Condition and Human Well-being Main Messages Many tools are available to assess ecosystem condition and support policy decisions that involve trade-offs among ecosystem services. Clearing forested land, for example, affects multiple ecosystem services (such as food production, biodiversity, carbon sequestration, and watershed protection), each of which affects human well-being (such as increased income from crops, reduced tourism value of biodiversity, and damage from downstream flooding). Assessing these trade-offs in the decision-making process requires scientifically based analysis to quantify the responses to different management alternatives. Scientific advances over the past few decades, particularly in computer modeling, remote sensing, and environmental economics, make it possible to assess these linkages. The availability and accuracy of data sources and methods for this assessment are unevenly distributed for different ecosystem services and geographic regions. Data on provisioning services, such as crop yield and timber production, are usually available. On the other hand, data on regulating, supporting, and cultural services such as nutrient cycling, climate regulation, or aesthetic value are seldom available, making it necessary to use indicators, model results, or extrapolations from case studies as proxies. Systematic data collection for carefully selected indicators reflecting trends in ecosystem condition and their services would provide an improved basis for future assessments. Methods for quantifying ecosystem responses are also uneven. Methods to estimate crop yield responses to fertilizer application, for example, are well developed. But methods to quantify relationships between ecosystem services and human well-being, such as the effects of deteriorating biodiversity on human disease, are at an earlier stage of development. Ecosystems respond to management changes on a range of time and space scales, and careful definition of the scales included in analyses is critical. Soil nutrient depletion, for example, occurs over decades and would not be captured in an analysis based on a shorter time period. Some of the impact of deforestation is felt in reduced water quality far downstream; an analysis that only considers the forest area itself would miss this impact. Ideally, analysis at varying scales would be carried out to assess trade-offs properly. In particular, it is essential to consider nonlinear responses of ecosystems to perturbations in analysis of trade-offs, such as loss of resilience to climate variability below a threshold number of plant species. Ecosystem condition is only one of many factors that affect human wellbeing, making it challenging to assess linkages between them. Health outcomes, for example, are the combined result of ecosystem condition, access to health care, economic status, and myriad other factors. Interpretations of trends in indicators of well-being must appropriately account for the full range of factors involved. The impacts of ecosystem change on well-being are often subtle, which is not to say unimportant; impacts need not be drastic to be significant. A small increase in food prices resulting from lower yields will affect many people, even if none starve as a result. Tracing these impacts is often difficult, particularly in aggregate analyses where the signal of the effect of ecosystem change is often hidden by multiple confounding factors. Analyses linking well-being and ecosystem condition are most easily carried out at a local scale, where the linkages can be most clearly identified. Ultimately, decisions about trade-offs in ecosystem services require balancing societal objectives, including utilitarian and non-utilitarian objectives, short-and long-term objectives, and local-and global-scale objectives. The analytical approach for this report aims to quantify, to the degree possible, the most important trade-offs within different ecosystems and among ecosystem services as input to weigh societal objectives based on comprehensive analysis of the full suite of ecosystem services.

Condition and Trends of Ecosystem Services and Biodiversity Main Messages The sub-global assessments show that several ecosystem services are in fair to poor condition and declining. Despite some gains in the provisioning of food, water, and wood, the capacity of ecosystems to continue to provide these services is at risk in several locations; problems with provisioning services include deterioration of water quality, deterioration of agricultural soils, and incapacity of supply to meet demand. Some threats affecting regulating services are loss of forest cover, rangeland degradation by overgrazing (particularly in drylands), loss of wetlands to urban development and agriculture, and change in fire frequency. Problems with cultural services include loss of cultural identity and negative impacts from tourism. Biodiversity is decreasing due to the loss of habitats and the reduction of species population sizes. Species declining particularly fast include species with large body size, species occupying high trophic levels, and species that are harvested by humans. In general, the assessments found the condition of water provisioning and biodiversity at global and sub-global scales to be congruent. However, in some cases, the sub-global assessments reported a poorer or better condition than the global findings for that region. Differences were due to the effects of drivers that were not picked up at the global scale, or to fine-scale heterogeneities missed in coarser-scale analyses at the global scale. There were more mismatches for biodiversity than for water provisioning because the concepts and measures of biodiversity were more diverse in the sub-global assessments. Land use change is the most important driver for provisioning, supporting, and regulating services and for biodiversity. Some direct drivers of ecosystem change were also indicators of the condition of the service (for example, harvest pressure is an indicator of biodiversity). Indirect drivers control the patterns of demand for provisioning and cultural services, thus inducing changes in ecosystems. Tourism was found to have a negative impact on biodiversity in the Northern Range, SAfMA, Portugal, and Caribbean Sea assessments. While human controlled drivers play a major role in determining the condition of ecosystem services, local biophysical constraints such as climate and soils also limit the production of ecosystem services. Clear trade-offs exist among ecosystem services. For example, a potential trade-off situation exists at one site in the southeastern part of the Gariep Basin, where biodiversity is totally irreplaceable and protein and caloric production are highly irreplaceable. The sub-global assessments, like the MA global assessment, found that an increase in provisioning services generally occurs at the expense of regulating services, supporting services, and biodiversity, or at the expense of the capacity of ecosystems to provide services to future generations. Trade-offs also occur among provisioning services such as between irrigated agriculture and freshwater provisioning.

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