Humans have greatly altered and impacted the global biosphere. We recognize now the importance of maintaining functioning ecosystem services both out of our own necessity and for the obligation we have to the eco-sphere. In 2000, the United Nations Secretary General called for a global ecological assessment, which was recently published as the Millennium Ecosystem Assessment (MEA) (www.mawed.org). The report compiled by over 1350 experts from 95 countries found that humans have changed ecosystems more rapidly and extensively over the last 50 years than in any comparable period of time in human history, resulting in a substantial and largely irreversible loss in the diversity of life on Earth (other highlights from the report are presented in Table 5). The MEA operated within a framework that identified four primary ecosystem services needed by humans: supporting (nutrient cycling, primary production, soil formation, etc.), provisioning (food, water, timber, fuel, etc.), regulating (climate, flood, disease, etc.), and cultural (esthetic, spiritual, educational, recreational, etc.). All have shown signs of stress and human pressures during the past century. One positive trend was the increase in food production (crops, livestock, and aquaculture), but this occurred with a concomitant loss of wild fisheries and food capture, along with a substantial increase in the resource inputs required to maintain the high agricultural production. While these observed changes to ecosystems have contributed to substantial net gain in human well-being and economic development, they have come at an increasing cost to the ecosystem health. The loss of this natural capital is typically not properly reflected in economic accounts.
Since the ecosystem provides the necessary functions for life, environmental management principles being devised and implemented today use the ecosystem concept as foundation. In particular, there have been several high-profile international efforts such as with the Convention on Biological Diversity (CBD), a treaty initiated in 1992 and signed by 150 government leaders with the expressed aim to protect and promote biological diversity and sustainable development. The 'ecosystem approach' adopted within this convention uses scientific methodologies regarding ecological interactions among organisms, their environment, and human activity to promote conservation, sustainability, and equity for managing natural resources. The approach deals with the complex socioecological-economic systems by promoting integrated assessment and adaptive management (see Panarchy). The ecosystem approach of the CBD is outlined below in 12 principles (Table 6). Note particularly principles 5-8 that deal with ecosystem functioning, and taken in the context of the other principles assert how this ecological functioning provides opportunities and constraints for economic and social well-being. Research in ecosystem ecology today is directed toward improved understanding of key issues such as ecosystem services, resilience, spatial and functional scale, time lags, dynamics, and indirect effects.
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