Skip to main content
main-content

Über dieses Buch

Globally, forest vegetation and soils are both major stores of terrestrial organic carbon, and major contributors to the annual cycling of carbon between the atmosphere and the biosphere. Forests are also a renewable resource, vital to the everyday existence of millions of people, since they provide food, shelter, fuel, raw materials and many other benefits. The combined effects of an expanding global population and increasing consumption of resources, however, may be seriously endangering both the extent and future sustainability of the world's forests. About thirty chapters cover four main themes: the role of forests in the global carbon cycle; effects of past, present and future changes in forest land use; the role of forest management, products and biomass on carbon cycling, and socio-economic impacts.

Inhaltsverzeichnis

Frontmatter

Introduction

Introduction

Throughout the world, forest ecosystems and their management are the focus of much human interest and concern. The traditional uses, as sources of food, shelter, construction materials and fuel, are as critical today as they ever were, while other values—such as havens for human relaxation and recreation, as wildlife habitats, and as maintainers of water supplies— have gained greater importance in many regions since the Industrial Revolution. But, as the 20th century draws to a close, additional values of global significance are increasingly being attributed to forests. One such attribute of the global forest resource is its ability to sequester atmospheric carbon. Examining the importance of this attribute and how it is influenced by human activities is, broadly speaking, the subject of this book.

Michael J. Apps, David T. Price

Forest ecosystems and the global carbon cycle

Frontmatter

2. Introduction

Transfer, storage and release of carbon (C) between the atmosphere and terrestrial and oceanic sinks typically occur over several different time scales. These processes are strongly dependent upon, and can potentially influence, the global climate. Part I is intended to provide a large-scale, long-term perspective on the role of forest ecosystems in the C cycle. The Working Group summary paper reports the group analysis of the extent to which climate variation over various time scales have influenced global terrestrial contributions to changes in the atmospheric C record. The individual articles review past changes in terrestrial C pools as determined from the observational record. They examine changes in the geologic past (e.g., due to long term shifts in climate), in the recent historical past (including the contributions of landuse change and deforestation) and contemporary 20th century trends (considering, for example, the effects of post-industrial pollution and large-scale tropical deforestation). Some Chapters also review current projections of ecosystem C dynamics into the foreseeable future.

Michael J. Apps, David T. Price

2. The global carbon cycle and the atmospheric record: “The problem definition”

The abundance of C02 in the atmosphere has increased from ~315 ppmv in 1958 to ~350 ppmv in the 1990s. The increase in the decade of the 1980s is ~55% of the C02 release from fossil fuel combustion, estimated at 5.5 Pg C yr-1, or ~40% of the total anthropogenic source, from fossil fuel combustion plus land use modification (estimated at 1.6 Pg C yr-1). Thus, mass balance requires the removal of ~60% of the anthropogenic C02 by the surface. The partitioning of the C02 sink between the ocean and land is a subject of intense debate and research. As the residence time of C02 in the terrestrial biosphere is much shorter than that in the ocean, C02 sequestered now in the terrestrial biosphere may be returned to the atmosphere in the next 50-100 years to accelerate greenhouse warming (see Woodwell 1995). Therefore, understanding the mechanisms responsible for the C02 uptake is crucial for projections of future C02 levels in the atmosphere.

Inez Fung

3. Nutrient constraints on carbon storage in forested ecosystems

Carbon (C) cycling in terrestrial ecosystems is inextricably linked to the cycles of essential nutrients like nitrogen (N) and phosphorus (P) (Bolin and Cook 1983; Melillo and Gosz 1983; Hobbie et al. 1984; Vitousek et al. 1988; Rastetter et al. 1991, 1992; Rastetter and Shaver 1992). Consequently, ecosystem C uptake and storage should be tightly constrained by the availability of these nutrients. In particular, both vegetation and soil micro-organisms must maintain a nutritional balance to survive. This nutritional balance sets limits on the amount of C that can be sequestered in an ecosystem with limited nutrient capital. From this perspective, changes in the amount of C sequestered in ecosystems must be accompanied by at least one of the following changes in the chemical properties of ecosystems (Rastetter et al. 1992):

Alan R. Townsend, Edward B. Rastetter

4. Estimated extent of forested peatlands and their role in the global carbon cycle

Wetlands are areas that are transitional between terrestrial and aquatic systems, where the water table is usually at or near the surface or the land is covered by shallow water (Cowardin et al. 1979). The definition of wetlands in Canada expresses a similar concept: wetlands are lands that have the water table at, near or above the land surface or which are saturated for a long enough period to promote wetland or aquatic processes as indicated by hydric soils, hydrophytic vegetation, and various kinds of biological activity that are adapted to the wet environment (Tarnocai 1980).

Stephen C. Zoltai, Pertti J. Martikainen

5. Sequestration of carbon in the Finnish boreal forest ecosystem managed for timber production

The increasing concentration of carbon dioxide (CO2) in the atmosphere alone contributes by over 50% to the enhancing greenhouse effect (Houghton et al. 1990, 1992). The major anthropogenic sources of carbon (C) entering the atmosphere are combustion of fossil fuels and land-use changes. Enhancement of the greenhouse effect can be mitigated by decreasing the emission of C or by increasing the capacity of terrestrial C sinks. Terrestrial C sinks can, in turn, be strengthened by increasing the C in vegetation or soil on the current land area or by increasing the area covered by vegetation. In this context, the role of forest ecosystems is crucial, since they occupy one third of the Earth’ land area and contain approximately 45% of the total terrestrial C (915 Pg C of 2050 Pg C) (Bolin 1986; Houghton et al. 1990).

Seppo Kellomäki, Timo Karjalainen

6. Carbon storage and climate change in Swedish forests: a comparison of static and dynamic modelling approaches

Changes in the global carbon (C) cycle caused by human activities have focused the attention of environmental scientists on where and how C is distributed through the terrestrial biosphere. Forests are the largest land reservoir for C (e.g., see Kellomäki and Karjalainen, Chapter 5). They also have the potential to be a C sink in the future. However, their future role in this respect depends not only on present and future management practices, but also on how the vegetation responds to climate changes that may already be underway.

Martin T. Sykes, I. Colin Prentice

7. Climate change and management of insect defoliators in boreal forest ecosystems

Insects are the most diverse group of terrestrial animals. Not surprisingly, they influence several ecosystem processes and thus have a profound influence in most terrestrial ecosystems by occupying a myriad o f niches. The reciprocal interaction of insects with forest plants includes some of the most finely tuned examples of mutualism known as well as some of the most destructive interactions between insects and plant populations. These interactions have important consequences to the development of forest ecosystems and insects may regulate forest productivity (Mattson and Addy 1975). Insects also have a more indirect role in forested ecosystems in that they are often important regulators of herbivore populations, may be important food items for vertebrate populations, and perform a significant function in nutrient cycling in concert with micro-organisms. (See also Chapter 15, Galinski and Witowski). However, both insects and plants are poikilotherms and thus their activities in forest ecosystems are regulated to a large extent by climate

W. Jan A. Volney

8. Some potential carbon budget implications of fire management in the boreal forest

Forest fire is a natural force that has shaped boreal and temperate forest ecosystems in the northern hemisphere for millennia, to the point that these forests have not only adapted to, but are dependent upon, periodic stand-replacement wildfires to maintain their existence. Over the past century people throughout northern forest ecosystems have coexisted, at times somewhat uneasily, with this important natural force, as fire management agencies attempted to balance public safety concerns and the industrial and recreational use of these forests, with costs, and the need for natural forest cycling through forest fires. In recent years fire management has been complicated by a growing recognition of the need to reconcile attempts to minimise fire losses with the growing cost of fire management and the beneficial impacts of fire. Canadian, Russian, and American fire managers have always designated parts of the boreal zone, usually in northern regions, as “lower priority” zones that receive little or no fire protection, since fires that occurred there were thought to have little or no significant detrimental impact on public safety and forest values. The realisation that total fire exclusion is neither possible nor ecologically desirable, initiated a gradual move toward the widespread adoption of fire management strategies that prioritise protection of high-value resources while permitting burning in more remote areas. This is particularly true in the boreal forest regions of Canada, Russia, and Alaska where lower population densities and forest use allow more flexible fire management strategies.

Brian J. Stocks, Bryan S. Lee, David L. Martell

9. WG1 Summary: Natural and anthropogenically-induced variations in terrestrial carbon balance

Combustion of fossil fuels and changes in land use have caused a substantial increase in atmospheric CO2 over the past century, yet the actual atmospheric change is only about half of total fossil fuel emissions alone. This difference is accounted for by carbon (C) uptake into terrestrial and oceanic systems (Table 9.1). CO2 dissolves into surface waters of the ocean, and can then be stored for centuries via transport into deep waters. Terrestrial ecosystems act as a sink for CO2 when their net ecosystem productivity (NEP) is positive, in other words when net primary productivity (NPP) exceeds heterotrophic respiration. Recent estimates suggest that significant C sinks are operating in both land and ocean systems (Tans et al. 1990; Keeling et al. 1993; Siegenthaler and Sarmiento 1993), but considerable uncertainty exists about the relative sizes of these sinks, about the mechanisms behind terrestrial storage, and about the potential for the terrestrial biosphere to continue moderating the accumulation of CO2 in the atmosphere.

Alan R. Townsend, Martin T. Sykes, Michael J. Apps, Inez Fung, Seppo Kellomäki, Pertti J. Martikainen, Edward B. Rastetter, Brian J. Stocks, W Jan A. Volney, Stephen C. Zoltai

The global carbon cycle and forest land use: past, present and future

Frontmatter

11. Introduction

Part II reviews the available information and contemporary understanding of past and present changes in global and regional terrestrial ecosystem carbon (C) pools, and of the C fluxes associated with forest management and land-use activities. Tropical, temperate and boreal forests are assessed separately, in recognition of the profound differences in their ecological dynamics and socio-economic pressures. The possibilties for managing existing forest ecosystems sustainably, and for reclamation of degraded forest lands, as C stores are examined. Some projections of future changes (under future climate and socio-economic scenarios) are also reviewed.

David T. Price, Michael J. Apps

10. Land-use change and terrestrial carbon: the temporal record

Understanding changes in the terrestrial pools of carbon (C) over the last two centuries helps identify management strategies that might be used to enhance the storage of C on land in the future. Three general types of management can be recognised. The first two: policies affecting the area of forests; and policies affecting the amount of C per unit area of forest, including the amount stored in forest products; are directly related to the management of land, particularly forests. The third type of management pertains to maintaining the climate of the Earth so as, again, to conserve and enhance both the area of forests and the amount of C stored per unit area of forest. Although the latter type of management is not related to land use or land-use change, perse, knowing the contribution of land-use change to the global C cycle over the last two centuries helps identify the critical role that forests may play in the future.

Richard A. Houghton

11. Tropical forests and the global carbon cycle: estimating state and change in biomass density

Tropical forests have an important role in the global carbon (C) cycle because of their existing large areal extent, high rates of deforestation, large C pool in vegetation and soil, and high rates of C emissions resulting from conversion to other uses (equivalent to between 22 and 37% of current fossil fuel C emissions) (Table 11.1). Tropical forests currently account for about 43% of the global forest area (Dixon et al. 1994), most of which is in tropical America (52%), followed by tropical Africa (30%) and tropical Asia (18%). They occur mostly as lowland formations where 88% are at an elevation of 1000 m or less. Within the lowlands, 47% are in the rain forest ecological zone, 38% in the moist deciduous zone, and 15% in the dry to very dry zone (Food and Agriculture Organization (FAO) 1993).

Sandra Brown

12. Carbon budget of the Russian boreal forests: a systems analysis approach to uncertainty

The total land area of the Russian boreal zone is 1527.6 Mha, including 1143.0 Mha of Forest Fund areas and 735.8 Mha of forested areas. These estimates are based on Forest State Account data (Goscomles SSSR 1990, 1991). Forest Fund areas include forest land and nonforest land. Forest land is in turn divided into forested areas, covered by closed forests, and unforested areas, designated for forests but temporarily without a forest (sparse forests, burnt areas and dead stands, grassy glades). Non-forest land is represented by unproductive land, such as bogs, rocks, sand, and glaciers, and by land with special uses (forest roads, water reservoirs, and relatively small areas of arable lands, pastures farms, etc., situated on Forest Fund areas). For a more detailed description see, e.g., Nilsson et al. (1992). Nearly 95% of all Russian closed forests are considered boreal. Thus, the Russian boreal forests play an important role in the global carbon (C) cycle

Anatoly Z. Shvidenko, Sten Nilsson, Vjacheslav A. Rojkov, Valentin V. Strakhov

13. Conflicting objectives while maximising carbon sequestration by forests

In the current debate on global climatic change, forests and forestry policies have gained much attention; in particular hope has been expressed that forestry policies have the potential to mitigate climatic change—at least partially (Sedjo and Solomon 1988; Sedjo 1989b; Johnson 1992; Kauppi 1992; Krapfenbauer 1992; Kurz et al. 1992; Marland and Marland 1992; Dewar 1993; King 1993; Turner et al. 1993; Wisniewski et al. 1993). Many issues however, are poorly understood and contradictory conclusions have been drawn by different authors (e.g., Harmon et al. 1990; Marland and Marland 1992). While some authors have demonstrated how much land would be needed, how great the economic costs of a full mitigation by such policies would be (Sedjo 1989a), and have even warned against costly premature actions (Sedjo 1989b), others have argued that any contribution is worthwhile (Marland and Marland 1992). Moreover, management options favouring carbon (C) sequestering are often discussed without considering potential conflicts with other objectives, such as wood production.

Andreas Fischlin

14. Retrospective assessment of carbon flows in Canadian boreal forests

The Canadian boreal forest is comprised largely of even-aged stands that for millennia have undergone cycles of disturbance (i.e., fires or insect-induced stand mortality) and regrowth. Previous studies of regional-scale carbon (C) budgets have assumed that, when averaged over a large area, forests not directly affected by human disturbance or land-use change are in steady state with regard to their net C exchange with the atmosphere (e.g., Houghton et al. 1983; Houghton et al. 1987). Underlying this assumption is the notion that, integrated over a large area, C uptake in forests regrowing after disturbance is balanced by C release from disturbances. The area of Canadian forests affected by disturbances varies between years and decades (Kurz et al. 1995) and therefore the assumption of a zero net balance between C uptake and release can, at best, be correct for some long-term average. Recent interest in the global C balance and the role of terrestrial ecosystems focuses on year-to-year variation and the record of the past decades (Sarmiento et al. 1992; Chapter 10, Houghton; Chapter 3, Townsend et al. ). Analyses of forest C budgets that do not rely on a priori assumptions of steady-state conditions are thus required.

Werner A. Kurz, Michael J. Apps

15. The carbon pulse resulting from forest dieback related to insect outbreaks: case study of a forest district in the Sudety Mountains (southwest Poland)

Increasing concern over the possible effect of air pollution on European forest ecosystems is very noticeable (for literature review see Schulze et al. 1989). The area of severe forest decline due to pollution was estimated to be less than 0.5% of the European forest area and was thus considered not to have had much impact on the forest resources of the continent (Kauppi et al. 1992). However, in the area of forest decline a decrease in growing stock and permanent deforestation is occurring. This decreases the carbon (C) storage in forest ecosystemsand causes CO2 release into the atmosphere.

Wojciech Galinski, Jan Witowski

16. Carbon budget of temperate zone forests during 1851-2050

The temperate zone covers lands in the mid-latitudes on five continents between the two other main biomes, the tropical and boreal zone (e.g., Heath et al. 1993). The human population has utilised forests for a long time in areas such as China and southern Europe. Only about half of the original forests have remained forested in the temperate zone, while the other half has been converted to other uses, mainly to agricultural and pastoral land. More recently and especially in the second half of this century, the emissions of CO2, SO2, N-oxides and other gases from energyy production and industry have changed the forest environment.

Pekka E. Kauppi

17. WG2 Summary: Forests and the global carbon cycle: past, present, and future role

Research efforts over the last decade or so on the interaction of human and natural disturbances on the carbon (C) dynamics of forests have increased our state of understanding about the role of forests in the global C cycle. However, at the same time new areas of uncertainty and new data gaps have emerged. In this chapter, we present areas of improved understanding, identify areas of uncertainty that require further research, identify new data needs, discuss the future role of forests in the global C cycle, and conclude with a discussion on the need for a system for tracking the C flux from changes in the cover, use, and management of forest lands. Material for this overview chapter is based for the most part on the chapters included in this Part of the book.

Sandra Brown, Anatoly Z. Shvidenko, Wojciech Galinski, Richard A. Houghton, Eric S. Kasischke, Pekka Kauppi, Werner A. Kurz, Ian A. Nalder, Vjacheslav A. Rojkov

The global carbon cycle, forest products and forest biomass

Frontmatter

20. Introduction

Whereas the Chapters in Part II presented a “top-down” view of the role of forests in the context of global C cycling, the articles in Part III look at the global consequences from the viewpoint of forest management and harvesting. Here, the contribution made by forest products to carbon storage is considered explicitly, and the consequences of forest management for these products on ecosystem C storage are examined. Several models and simulation results are reported that provide estimates of the carbon stored in regional forests and wood products today and potential changes in the foreseeable future. The importance of considering fossil energy displacement (through both direct and indirect substitution) when assessing the C offset benefits of using forests and wood products to mitigate fossil-fuel emissions was a recurrent theme in the working group discussions and appears in a number of the Chapters. Another key issue addressed by Part III is the need for comprehensive methods to assess forest C budgets and to subject them to rigorous comparison.

David T. Price, Michael J. Apps

18. Carbon implications of forest management strategies

Forest management is frequently cited (e.g., Winjum et al. 1993; Kolchugina and Vinson 1993; U.S. Office of Technology Assessment 1991) as a strategy for attempting to ameliorate the build-up of the greenhouse gas CO2 in the Earth’s atmosphere. Combustion of fossil fuels is the primary cause of the atmospheric increase of CO2, with additional emissions coming from the clearing of forests to accommodate other land uses. The management of forests and forest resources can affect the global cycling of C in several ways. The amount of CO2in the atmosphere can be altered by changing:

Bernhard Schlamadinger, Gregg Marland

19. The influence of carbon budget methodology on assessments of the impacts of forest management on the carbon balance

There is now a substantial body of literature in scientific journals on the carbon (C) balance of forest ecosystems at all geographical scales, and some authors have proposed changes in the way forests are managed in order to enhance the offsetting or reduction of emissions of C to the atmosphere. As yet, however, there is no widely accepted and applied method for estimating the C budget of forests and the impacts of forest management on C sequestration. This paper describes how the results of C budgeting exercises depend strongly on the methodologies employed, and briefly considers the scope for developing conventions for the calculation and presentation of C budgets for forest ecosystems and forestry projects. These points are illustrated using examples of model simulations of the effects of alternative methods of forest management in Britain, and by comparison of published results of studies in other countries based on different C budgeting methodologies.

Robert Matthews

20. Significance of wood products in forest sector carbon balances

Global forests are thought to be important in mitigating the increase in atmospheric carbon dioxide (Dixon et al. 1991; Kauppi et al. 1992; Sampson et al. 1993). The gross global fluxes of CO2 between the atmosphere, biosphere and oceans are huge compared to the net annual increase in atmospheric CO2. This suggests that relatively small changes in these gross vegetation-atmosphere fluxes might change the net increase in the atmospheric CO2 concentration. To elucidate, very many studies have focused on the role of the biosphere in the global carbon (C) cycle (Apps et al. 1993; Armentano and Ralston 1980; Auclair and Bedford 1993; Houghton 1991; Lugo and Brown 1992; Sedjo 1992; Tans et al. 1990) and on the C sequestering potential of different forest types (Brown et al. 1985; Dewar and Cannell 1992; Dixon et al. 1991; Mohren and Klein-Goldewijk 1990a; Nabuurs and Mohren 1993; Schroeder and Ladd 1991; Winjum et al. 1992).

Gert-Jan Nabuurs

21. Plantation forestry-its role as a carbon sink: conclusions from calculations based on New Zealand’s planted forest estate

It is common to encounter misunderstanding with regard to the role of forests as a means of mitigating the postulated enhanced greenhouse effect (Houghton et al. 1990, 1992). Some of the confusion appears to lie in loose terminology. In particular, the words carbon sink, and carbon reservoir need to be clearly distinguished (see Glossary). Only if a reservoir increases in capacity does it constitute a net sink, and then only for the period during which it is expanding in size. The word store, used as a noun, may be synonymous with reservoir, but as a verb it means to create a reservoir or to act as a sink; hence use of store should be avoided. Confusion also surrounds the word forest, which is frequently used synonymously with stand. Forestry terms used throughout this chapter will be as defined by the Society of American Foresters (1917) and by Ford-Robertson (1971); more important terms are italicized upon first use and definitions provided in the Glossary. Whereas a stand comprises trees of similar composition, age-structure and management regime, a forest is a larger unit that may consist of hundreds or thousands of stands. The dynamics of a forest are considerably more complex than those of a stand, as shall be explained later.

J. Piers Maclaren

22. Carbon pools and fluxes in U.S. forest products

Increasing recognition that anthropogenic CO2 and other greenhouse gas emissions may effect climate change has prompted research studies on global carbon (C) budgets and international agreements for action. At the United Nations Conference on Environment and Development in 1992, world leaders and citizens gathered and initiated the Framework Convention for Climate Change (FCCC), an agreement to address global climate change concerns. Over 160 nations have signed the FCCC, whose ultimate goal is to stabilise the atmospheric concentration of greenhouse gases to prevent significantly negative effects on the climate system. To reach this goal, some nations, including the United States, have committed to reduce greenhouse gas emissions to 1990 levels by the year 2000. Knowledge of the magnitude and processes in C cycles is essential in developing effective strategies to mitigate anthropogenic emissions.

Linda S. Heath, Richard A. Birdsey, Clark Row, Andrew J. Plantinga

23. Effects of forest management, harvesting and wood processing on ecosystem carbon dynamics: a boreal case study

Many northern forests are managed with the objective of achieving and maintaining sustained yield. Sustained yield management implies continuous production so planned as to achieve at the earliest practical time, a balance between annual growth and harvesting. It is often argued that with silvicultural prescriptions, and protection from natural disturbances, responsible management will allow wood harvests and other benefits to be elevated in the long term, and thereafter maintained at increased levels indefinitely (when compared to unmanaged forest growing in a similar environment)

David T. Price, Ralph M. Mair, Werner A. Kurz, Michael J. Apps

24. WG3 Summary: Evaluating the role of forest management and forest products in the carbon cycle

Decisions on land-use and forest management can have a significant effect on the global carbon (C) budget. In order to evaluate the effect of land use and forest management decisions on the global C balance, or to assess the potential for positive change, we need not only to evaluate the current and near-term status of forests, but also to understand the processes and sectors, both ecological and industrial, that are affected by forest management decisions.

Robert W. Matthews, Gert-Jan Nabuurs, Vladislav Alexeyev, Richard A. Birdsey, Andreas Fischlin, J. Piers Maclaren, Gregg Marland, David T. Price

The human dimension: the global carbon cycle and socio-economics

Frontmatter

28. Introduction

Members of Working Group 4 attempted to account for human needs and impacts in the understanding of the role of forests in the global carbon (C) cycle. A major factor in the postindustrial era is the rapidly expanding human population, and the attendant acceleration of landuse change which directly influences C storage in global forests, particularly in the tropics. The important roles of forest ecosystems and their management are increasingly being recognised in global strategies proposed to mitigate the effects of anticipated climate change. Many of these strategies however, focus entirely on the biophysical aspects of the problem while ignoring human needs, and in the opinions of some, ignoring the socio-economic realities facing developing and developed countries alike. If human needs are not fully considered in international policy and management decisions relating to the world’s forests, it is likely there will be increased suffering and this will cause greater problems, both within and between countries, hence delaying or even destroying the opportunity for progress.

Michael J. Apps, David T. Price

25. The economics of increased carbon storage through plantations and forest management

Forest plantations offer what appear to be one of the more attractive approaches to sequester atmospheric carbon (C). They are attractive because: (1) studies have indicated that forests have the potential to sequester large amounts of C; (2) the technology for establishing new forests exists; (3) forests have a number of environmental benefits aside from C sequestration; and (4) most studies indicate that the costs of C sequestration using forests are quite modest

Roger A. Sedjo

26. Costs of forest-sector mitigation options

Carbon emissions from the forest sector are unevenly distributed across latitudes. Forests from the high- and mid-latitudes are estimated to be sequestering net C on the order of 0.70 ±0.2 Pg yr-1 (Dixon et al. 1994). The low-latitude countries, which are mostly developing nations, are the primary sources of net C emissions, estimated at 1.6 ±0.4 Pg yr-1 —a significant amount, which exceeds the net 1990 C emissions from the United States. The forest sector C emissions vary considerably amongst individual countries so that some are a net C sink (e.g., India) and others are a large net C source (e.g., Brazil) (Makundi et al. 1992).

Jayant Sathaye

27. Integrating the socio-economic and physical dimensions of degraded tropical lands in global climate change mitigation assessments

Models of global environmental change need to integrate its socio-economic and physical environmental dimensions much better than they do at present. The traditional separation between the social and environmental sciences has hindered development of interdisciplinary methodologies and led to predominantly physical assessments of key problem areas, such as the potential to mitigate global climate change by sequestering more terrestrial carbon (C) in woody biomass.

Alan Grainger

28. Socio-economic factors in the management of tropical forests for carbon

Tropical forest management response options to global warming include sustained harvest of timber, extraction of non-timber forest products, silvicultural plantations, agroforestry, managed secondary succession and forest maintenance (including both reserve protection and policy changes affecting deforestation). Socio-economic factors affect C management projects, and vice versa, and can negate C benefits and cause hardship for local populations. Forest maintenance has significant C benefits, as well as other environmental and social advantages. Prerequisites include understanding causes of deforestation.

Philip M. Fearnside

29. Economic aspects of carbon sequestration—some findings from Norway

Increased forest biomass to sequester carbon (C) has been one of several measures proposed to reduce the concentration of greenhouse gases in the atmosphere (cf. Dyson 1977; Sedjo 1990; EPA 1990; Cline 1992).

Birger Solberg, Hans Fredrik Hoen

30. People and forests in Canada: fitting carbon into a perplexing future

This is a strong statement, and no doubt there are many who believe it to be true. Indeed, there are likely many who want to see carbon (C) take a meaningful place within the substance of management objectives for Canadian forests. However, Pollard himself expresses some doubt in his conclusion:

Peter N. Duinker

31. Forests and global carbon management: a policy perspective

The human population has increased from 1.6 x 109 at the beginning of the 20th century to some 5.6 x 109 today. Associated with this increase, industrialisation and economic growth has increased per capita consumption of natural resources leading to increased pollution of air, soil and water resources. Increasing levels of environmental degradation have raised concerns for environmentally sustainable development. Of particular concern is the loss and rate of loss of global forests and their ability to meet the increasing needs of an expanding population. Because of this concern forests have emerged as one of the key items on national and international political and policy agendas.

Robert B. Stewart, Jagmohan S. Maini

32. WG4 Summary: Human dimensions of the forest-carbon issue

The preceding discussions have dealt with basic biophysical processes associated with forests and the global carbon (C) cycle, and the technical feasibilities of intervening in those processes so that forests play a stronger role in sequestering C from the atmosphere. Such discussions are a vital component of a full understanding of how humanity might mitigate what we shall call the C problem—what will it take to manage and use forests to lessen climatic change due to increasing atmospheric CO2? Any meaningful answer requires that we put the technical possibilities into the social, economic, institutional and political contexts within which all human endeavour takes place. Are these contexts—current and future— facilitative of strong implementation of the technically feasible actions, or will they pose constraints? If the latter, what will it take to remove the barriers?

Peter N. Duinker, Roger A. Sedjo, Philip M. Fearnside, Alan Grainger, Jayant Sathaye, Birger Solberg, Robert B. Stewart, Valentin V. Strakhov, George M. Woodwell

Concluding remarks

Frontmatter

33. Summary

Global forests are complex dynamic systems that both respond to, and create physical feedbacks to, the global environment. Systematic global change imposed upon the biosphere will therefore undoubtedly cause responses in forest ecosystems, with potential consequences that cannot be predicted in detail. These consequences will almost certainly contribute to further environmental and socio-economic impacts, of which some will be deleterious for the human habitat. Among these will be major changes to global forest carbon (C) dynamics, with regional shifts in C sequestration and release, linked to gains or losses in net ecosystem productivity (NEP). It is doubtful whether global NEP would be truly zero when averaged over the planetary surface and over long time periods—even in the absence of the human species. It is therefore virtually certain that, given the current situation of accelerating anthropogenic changes, global average NEP is also undergoing significant change. Resolving the magnitude and direction of this change however, even for specific geographic regions, will continue to be a complex and challenging problem.

David T. Price, Michael J. Apps

34. Epilogue: Forests and the human habitat: the case for building a global consensus

In the midst of the heady political changes that have marked the early years of this decade, including the end of the cold war, the reunion of the two Germany’s, and the rekindling of dormant ancient hatreds and ambitions in Yugoslavia, Rwanda-Burundi and elsewhere, the world has discovered a series of emergent global environmental problems for which there is no precedent and no cure short of a degree of global co-operation never previously sought or achieved. Success in addressing them offers the world virtually unlimited prospects for further improvement of the human enterprise; failure offers a bleak future beset by intensified tribal clashes over the bare necessities of life as the human habitat becomes progressively impoverished. In acknowledgement of this dilemma, articulated so sharply as the need for sustainable development by the Brundtland Commission, the United Nations Conference on Environment and Development attempted to prepare three international conventions for adoption at the June 1992 meetings in Brazil. The topics were the atmosphere, biodiversity, and forests. As we outline below, success in addressing the atmosphere and biodiversity depends on success in addressing forests, the topic on which the least progress was made.

George M. Woodwell, Kilaparti Ramakrishna

Backmatter

Weitere Informationen