5 Ecosystems and Their Goods and Services HABIBA GITAY (AUSTRALIA), SANDRA BROWN (USA), WILLIAM EASTERLING (USA), AND BUBU JALLOW (THE GAMBIA) Lead Authors: J. Antle (USA), M. Apps (Canada), R. Beamish (Canada), T. Chapin (USA), W. Cramer (Germany), J. Frangi (Argentina), J. Laine (Finland), Lin Erda (China), J. Magnuson (USA), I. Noble (Australia), J. Price (USA), T. Prowse (Canada), T. Root (USA), E. Schulze (Germany), O. Sirotenko (Russia), B. Sohngen (USA), J. Soussana (France) Contributing Authors: H. Bugmann (Switzerland), C. Egorov (Russia), M. Finlayson (Australia), R. Fleming (Canada), W. Fraser (USA), L. Hahn (USA), K. Hall (USA), M. Howden (Australia), M. Hutchins (USA), J. Ingram (UK), Ju Hui (China), G. Masters (UK), P. Megonigal (USA), J. Morgan (USA), N. Myers (UK), R. Neilson (USA), S. Page (UK), C. Parmesan (USA), J. Rieley (UK), N. Roulet (Canada), G. Takle (USA), J. van Minnen (The Netherlands), D. Williams (Canada), T. Williamson (Canada), K. Wilson (USA) Review Editors: A. Fischlin (Switzerland) and S. Diaz (Argentina) CONTENTS Executive Summary 23 7 5. 6 . Fo r ests and Woo d l a n d s 28 6 5. 6 . 1 . Current Status and Tre n d s 28 7 5. 1 In t r oduction and Scope 24 3 5. 6 . 2 . Pressures on Forests and Woo d l a n d s 28 9 5. 6 . 3 . Responses by Forests and Woo d l a n d s 5. 2 Ef fects of Global Change on and Impacts on their Goods and Services 29 3 the Ter r estrial Biosphere and its Uses 24 4 5. 6 . 4 . Adaptation Options and Vul n e r a b i l i t y 5. 2 . 1 . Observational Studies 24 6 of Forests and Woo d l a n d s 29 5 5. 2 . 2 . Current Models of Ecosystem Change 24 7 5. 2 . 3 . Impacts on Biodiversity 25 0 5. 7 . Lakes and Strea m s 29 6 5. 2 . 4 . Ch a l l e n g e s 25 1 5. 7 . 1 . Status of Goods and Services 29 7 5. 7 . 2 Pressures on Goods and Services 29 8 5. 3 . Ag r i c u l t u r e 25 2 5. 7 . 3 Responses of Lakes and Streams 5. 3 . 1 . State of the Global Agricultural Sector 25 3 and Impacts on their Goods and Services 29 8 5. 3 . 2 . Pressures on Agriculture Sector 25 3 5. 7 . 4 Adaptation Options 30 3 5. 3 . 3 . Response of Crops and Livestock 5.7.5 Vul n e r a b i l i t y 30 4 and Impacts on Food and Fiber 25 4 5. 3 . 4 . Impact and Adaptation at Farm 5. 8 . Inland Wet l a n d s 30 4 to Subnational Regional Scales 25 8 5. 8 . 1 . State of Wetland Services 30 5 5. 3 . 5 . Modeling Impacts and Ad a p t a t i o n 5. 8 . 2 . Pressures on Wetland Services 30 6 in a Global Economy 26 9 5. 8 . 3 . Impacts on Wetland Services 30 7 5. 3 . 6 . Vulnerability of the Agricultural Sector 27 0 5. 8 . 4 . Adaptation Options for Wet l a n d s 31 1 5. 8 . 5 . Vulnerability of Functions and 5. 4 . Wildlife in Ecosystems 27 1 Key Services of Wet l a n d s 31 1 5. 4 . 1 . State of Wil d l i f e 27 1 5. 4 . 2 . Pressures on Wil d l i f e 27 2 5. 9 . Ar ctic and Alpine Ecosystems 31 1 5. 4 . 3 . Responses of Wildlife and 5. 9 . 1 . State and Trends of Goods and Services 31 1 Impacts on Goods and Services 27 3 5. 9 . 2 . Responses of Arctic and Alpine Ecosystems 5. 4 . 4 . Adaptation by Humans and Impacts on their Goods and Services 31 2 for Changes in Goods and Services 27 8 5. 9 . 3 . Adaptation Options 31 3 5. 4 . 5 . Equity Issues 28 0 5. 9 . 4 . Vul n e r a b i l i t y 31 4 5. 4 . 6 . Vulnerabilities, Sensitivities, Uncertainties 28 0 5. 1 0 . Re s e a r ch Needs across Ecosystems 31 4 5. 5 . Rangelands (Grasslands, Savannas, and Deserts ) 28 0 5. 5 . 1 . Current Status of Key Goods and Services 28 1 Ac k n o w l e d g m e n t s 31 5 5. 5 . 2 . Major Pressures on Key Goods and Services 28 1 5. 5 . 3 . Responses of Rangelands and Re f e re n c e s 31 5 Impacts on Goods and Services 28 1 5. 5 . 4 . Adaptation Options 28 5 5. 5 . 5 . Vulnerabilities and Sensitivity to Climate Change 28 6 EXECUTIVE SUMMARY Ecosystems are subject to many pressures (e.g., land-use Although the beneficial effects of elevated CO2 on the change, resource demands, population changes); their extent yield of crops are well established for the experimental and pattern of distribution is changing, and landscapes are conditions tested, this knowledge is incomplete for numerous becoming more fragmented. Climate change constitutes an tropical crop species and for crops grown under suboptimal additional pressure that could change or endanger ecosystems conditions (low nutrients, weeds, pests and diseases). In and the many goods and services they provide. experimental work, grain and forage quality declines with CO 2 enrichment and higher temperatures (high confidence) There now is a substantial core of observational and experimental (see Sections 5.3.3, 5.4.3, and 5.5.3). studies demonstrating the link between climate and biological • Experimental evidence suggests that relative enhancement or physical processes in ecosystems (e.g., shifting range of productivity caused by elevated CO2 usually is greater boundaries, flowering time or migration times, ice break-up on under drought conditions than in wet soil. Nevertheless, a streams and rivers), most evident in high latitudes. Recent climate change-induced reduction in summer soil moisture modeling studies continue to show the potential for significant (see Table 3-10)—which may occur even in some cases of disruption of ecosystems under climate change. Further increased summer precipitation—would have detrimental d e v e lopment of simple correlative models that were available effects on some of the major crops, especially in drought- at the time of the Second Assessment Report (SAR) point to prone regions (medium confidence). areas where ecosystem disruption and the potential for ecosystem • Soil properties and processes—including organic matter migration are high. Observational data and newer dynamic decomposition, leaching, and soil water regimes—will be vegetation models linked to transient climate models are influenced by temperature increase (high confidence). Soil r e f i ning the projections. However, the precise outcomes erosion and degradation are likely to aggravate the detrimental depend on processes that are too subtle to be fully captured by effects of a rise in air temperature on crop yields. Climate current models. change may increase erosion in some regions, through heavy rainfall and through increased windspeed (competing At the time of the SAR, the interaction between elevated carbon explanations) (see Section 5.3.3). dioxide (CO2), increasing temperatures, and soil moisture • Model simulations of wheat growth indicate that greater changes suggested a possible increase in plant productivity variation in temperature (change in frequency of extremes) through increased water-use efficiency (WUE). Recent results under a changing climate reduces average grain yield. suggest that the gains might be small under field conditions Moreover, recent research emphasizes the importance of and could be further reduced by human management activities. understanding how variability interacts with changes in Many ecosystems are sensitive to the frequency of El Niño- climate means in determining yields (established but Southern Oscillation (ENSO) and other extreme events that incomplete) (see Section 5.3.4). result in changes in productivity and disturbance regimes (e.g., • Crop modeling studies that compare equilibrium scenarios fires, pest and disease outbreak). with transient scenarios of climate change report significant yield differences. The few studies that include comparable transient and equilibrium climate change scenarios generally Agriculture report greater yield loss with equilibrium climate change than with the equivalent transient climate change. Even these Most global and regional economic studies—with and without few studies are plagued with problems of inconsistency in climate change—indicate that the downward trend in real methodologies, which make comparisons speculative at co m modity prices in the 20th century is likely to continue into this time (see Section 5.3.4). the 21st century, although confidence in these predictions decreases farther into the future (see Section 5.3.1). Adaptation and Vulnerability Impacts • Prospects for adaptation of plant material to increased air temperature through traditional breeding and genetic • Experiments have shown that relative enhancement of m o dification appear promising (established but incomplete). productivity caused by elevated CO2 usually is greater More research on possible adaptation of crop species to when temperature rises but may be less for crop yields at elevated CO2 is needed before more certain results can be above-optimal temperatures (established but incomplete). presented (see Section 5.3.3). 238 Ecosystems and Their Goods and Services • Simulations without adaptation suggest more consistent • It is concluded with low confidence that a global temperature yield losses from climate change in tropical latitudes than rise of greater than 2.5°C will result in rising commodity temperate latitudes. Agronomic adaptation abates extreme prices. Similarly, a global temperature rise of greater than yield losses at all latitudes, but yields tend to remain beneath 2.5ºC increases by 80 million the absolute number of baseline levels after adaptation more consistently in the p e ople at risk of hunger.