VI.5 Forests
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VI.5 Forests Luis A. Solórzano and Guayana I. Páez-Acosta OUTLINE 1. Forests and people: A long history in brief 2. Forest ecosystem services: Types and scales of delivery 3. Provisioning services: Harvest of forest products 4. Regulating services: Benefits from forests’ functioning 5. Cultural services: Benefits from forests’ subtle values 6. Reduction of world’s forests: Prospective supply Forest ecosystem services by definition are dependent on the use and value assigned to them by people’s needs and perceptions. Humans have historically interacted with forested biomes around the globe and changed their ecological structure as well as their flow of services; consequently, forest biological states, human uses, and anthropocentrically assigned values have changed throughout human history. Although global demand for forest products and services has continuously increased, the impoverishment of the world’s forests continues, and their future capacity to support human needs is at risk. GLOSSARY anthropocentrism. A human-centered perception and explanation of any given system, e.g., assessing a tropical forest in terms of timber value is an environmental anthropocentric perspective. biotic impoverishment. The generalized series of transitions that occur in the structure and function of ecosystems under chronic elevated disturbance. critical habitat. The ecosystems on which any target species—e.g., endangered and threatened pollinators —depend. environmental uncertainty. Unpredictable sources of density-independent changes in population level parameters . forest ecosystem management. An approach to maintaining or restoring the composition, structure, and function of natural and modified forests, based on a collaborative vision that integrates ecological , socioeconomic, and institutional perspectives , applied within naturally defined ecological boundaries. forest fragmentation. Disruption of extensive forest habitats into isolated, smaller patches. resilience. The capacity of an ecosystem to tolerate disturbance without collapsing into a qualitatively different state that is controlled by a different set of processes. Resilience has three defining characteristics : the amount of change the system can undergo and still retain the same controls on function and structure; the degree to which the system is capable of self-organization; and the ability to build and increase the capacity for learning and adaptation. scale. The magnitude of a region or process, involving both spatial size and temporal rates. 1. FORESTS AND PEOPLE: A LONG HISTORY IN BRIEF Even before the development of agriculture, human hunter-gatherers made their way onto all continents, except Antarctica, and selectively consumed and settled in forested regions. Historical evidence confirms the growth and later collapse of ancient civilizations as their forests were used, impoverished, and ultimately degraded. At the onset of Western civilization, massive and destructive forest-use patterns were repeated in Syria, Persia, Greece, and North Africa and later in Rome. The same seems to have occurred in Central America with the Mayan civilization. There are examples in contemporary nations as well, where overpopulation and deforestation have degraded landscapes to uninhabitable stages; this in turn contributed to social crises and made it difficult to create or maintain stable economic and political systems. Human use of forests over the last 8000 to 10,000 years has led to a world where today 25 countries are completely deforested and another 29 have lost more than 90% of their forest cover. At the beginning of the twenty-first century , the human population surpassed 6 billion, and dependency on forest products and services not only is still vital but continuously grows in magnitude and type, while forest use and deforestation have dramatically intensified since the second half of the last century. Today, virtually all major watersheds globally suffer some degree of disruption from forest clearing . Seeking economic growth and development, many countries are repeating forest-clearing patterns experienced by developed countries at much earlier times. Direct deforestation or climate-related forest droughts, fires, impoverishment, and degradation processes occur across extensive regions in China, India, Pakistan , Russia, Southeast Asia, the Philippines, Java, Central America, and South America—mainly in the Amazon. 2. FOREST ECOSYSTEM SERVICES: TYPES AND SCALES OF DELIVERY Forests and their functioning depend on processes that take place over a range of spatial and temporal scales; consequently, their ecosystem services are generated at several ecological scales as well. Essential ecological , biogeochemical, hydrologic, and climate functions naturally performed by forest ecosystems have historically provided services to humanity at scales varying from short-term, site levels (e.g., food) and medium-term, regional levels (e.g., landscape-level hydrologicand climatic stability)tolong-term, globallevels (e.g., carbon sequestration). In terms of human use, the types of services...


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