| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Extent of current grasslands | Land cover characterization developed by International Geosphere/Biosphere Program (IGBP) using global satellite data at l-km resolution (GLCCD 1998), modified by WRI using Olson (1994a and b); WRI global, electronic dataset of watersheds of the world (Revenga et al. 1998) |
| Extent of dry grasslands | Aridity zones of the world mapped by United Nations Environment Programme according to the ratio of mean annual precipitation to mean annual potential evapotranspiration (UNEP 1992, 1997). |
| Extent of woody vegetation | Land cover characterization developed by University of Maryland Geography Department identifying percent woody and herbaceous cover across the world’s terrestrial surface (DeFries et al. 2000). |
| Extent of historical grassland | Major habitat types of the world representing geographic areas of similar environmental conditions before major modification by humans (WWF-U.S. 1999). |
| Trends in grassland conversion | Regional data reported by United States Geological Survey (USGS) and the Nature Conservancy (TNC) for North America; IUCN – The World Conservation Union for Europe; State of the Environment Advisory Council for Australia; United States Agency for International Development (USAID) for Kenya. |
| Modification of grasslands | Agriculture GLCCD (1998) land cover characterization as modified by PAGE; methodology may over-represent grassland modification in some parts of the world, such as southern Africa. |
| Urbanization/Human settlements | Population data from inventory of national censuses (CIESIN 2000); see also see below for road fragmentation using Digital Chart of the World road’s database (ESRI 1993). |
| Desertification | Use of aridity zones and human population data to describe effects of land degradation in dry areas as presented in the World Atlas of Desertification (UNEP 1992, 1997) Fire Satellite data from European Space Agency (ESA) for fires in Africa, Latin America, SE Asia, and Oceania detected during 1993 (Arino and Melinotte 1997). |
| Domestic livestock | Various studies in scientific literature; datasets from FAO and ILRI described in chapter on food, forage and livestock. |
| Fragmentation | Fragmentation index developed by the World Wildlife Fund (Dinerstein et al. 1995; Ricketts et al 1997); spatial, electronic database of road networks worldwide from Digital Chart of the World (DCW) (ESRI 1993) presented in chapter on biodiversity. |
| Non-Native Species | Dataset for North America compiled by WWF-US (Ricketts et al. 1997), described in chapter on biodiversity. |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
| ♦ Grasslands cover
some 40 percent of the earth’s surface (excluding Greenland and
Antarctica). ♦ Grasslands are found in every region of the world; Sub-Saharan Africa and Asia have the largest total area in grassland, 14.5 and 8.9 million km2 respectively. ♦ The five countries with the largest grassland area are Australia, the Russian Federation, China, the United States, and Canada. ♦ The five countries with the highest percentage of grassland area, all in Sub-Saharan Africa, are Benin, Central African Republic, Botswana, Togo, and Somalia. ♦ Twenty-five of the 145 major watersheds of the world are made up of at least 50 percent grassland. Sub-Saharan Africa has the most extensive grassland watersheds; Europe, the least. ♦ Grasslands are found most commonly in semi-arid zones (28 percent of the world’s grasslands), followed by humid (23 percent), cold (20 percent), and arid zones (19 percent). ♦ Human populations are highest in the dry grasslands (arid, semi-arid, and dry sub-humid) of Sub-Saharan Africa followed by Asia. Human populations are lowest in the dry grasslands of Oceania. ♦ Temperate grasslands, savannas, and shrublands have experienced heavy conversion to agriculture, more so than other grassland types including tropical and subtropical grasslands, savannas, and woodlands. |
♦ Global estimates of grasslands
are complicated by diverse definitions
of grassland, and variability in the designation of boundaries between
land cover types. ♦ Higher-resolution satellite data, available now and expected to become more accessible within the next few years, could improve the information base. These data, however, will most likely remain expensive to obtain, especially for extensive areas. ♦ Expansion of our knowledge of grassland condition is hindered by disagreement on the characteristics of a healthy grassland ecosystem and the difficulty of identifying the best methods to determine ecosystem health. ♦ Various satellite sources primarily from the U.S. and Europe are being perfected to better detect, monitor and analyze fires over time. NASA’s website presents current (1999-2000) fire counts and additional fire information at 4km resolution in monthly intervals but these data are not yet available for general analysis. Studies using these data are required to analyze the long-term effects of frequent fires on grassland systems. |
| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Soil degradation | Global Assessment of the Status of Human-Induced Soil Degradation (GLASOD), spatial, electronic data at 1:10 million; Soil Degradation Assessment for South and Southeast Asia (ASSOD) at 1:5 million (UNEP 1992 and 1997). |
| Vegetation change | Global satellite imagery; surface reflectance data from NOAA/AVHRR that provides the Normalized Difference Vegetation Index (NDVI); various models using climate and vegetation data to analyze Net Primary Productivity (NPP); University of Maryland Geography Department’s Global Production Efficiency Model (GLOPEM); Rain-Use Efficiency (RUE) Index using data from rainfall stations to indicate regional trends (UNEP 1997; Cramer and Field 1999; Prince et al 1998; Goetz et al 1999). |
| Livestock densities | Spatial, electronic data on livestock populations of the world (Lerner and Matthews 1988); regional spatial coverage of Africa by country and other administrative units from the International Livestock Research Institute (ILRI) (Kruska et al.1995). |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
| ♦ Although much of
the PAGE grassland area does not coincide with
mapping units that are degraded according to GLASOD extent and degree
classes, nearly 49 percent are lightly to moderately degraded and at
least 5 percent are considered strongly to extremely degraded. ♦ Satellite imagery has greatly expanded our ability to measure grassland vegetation. Promising measures for determining grassland condition are long-term trends in NDVI, NPP, and RUE. ♦ Trends in RUE provide a potential method of separating vegetation declines due to lack of rainfall from declines associated with degradation. Combining this index with other measures, such as livestock densities, may increase our ability to more accurately evaluate grassland condition. ♦ While some grasslands support high livestock densities, association of grassland condition with specific livestock densities must be based in part on information about geographic location and management practices as well as on characteristics of the soil, vegetation, and wildlife. |
♦ Soil condition is key to
evaluating grassland condition; GLASOD
provides the only global database on soil degradation. It is heavily
criticized, however, for relying on qualitative data interpreted in
different ways and produced at too large a scale for assessing
degradation at the national level. ASSOD is an improvement over GLASOD,
but its 1:5 million scale is still too coarse on which to base national
policies. We need a worldwide digital database of soil degradation at
1:1 million backed up by field reconnaissance. ♦ To take advantage of improved satellite data for monitoring vegetation change, we need continued evaluation of NPP models, compilation of long-term trends, and further evaluation of the use of additional indicators (such as RUE) in the assessment of grassland ecosystem condition. ♦ Relationships among meat production, livestock densities, and rangeland condition must be assessed with caution. They require worldwide spatial data that differentiate feedlot from range-fed livestock, identify management practices, and report population levels of all livestock—domestic and wild. |
| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Areas of designated importance | Centers of Plant Diversity Compilation of information on centers of plant diversity worldwide through fieldwork and expert judgment from IUCN-The World Conservation Union, spatial, electronic database by World Wildlife Fund (WWF-U.S) (Davis et al 1994 and 1995). |
| Endemic Bird Areas | Worldwide documentation of breeding ranges of restricted-range bird species developed by Birdlife International through fieldwork and expert judgment (Stattersfield et al 1998). |
| Global 200 Ecoregions | Designation of 200–plus ecoregions in the world by WWF-U.S., selected as outstanding examples of diverse ecosystems based on expert opinion (Olson and Dinerstein 1998). |
| Biological Distinctiveness Index | Index of ecoregions based on species richness, species endemism, rarity of habitat type, rare phenomena, and beta diversity developed by WWF-U.S. for North and Latin America (Dinerstein et al. 1995, Ricketts et al 1999). |
| Protected Areas | Global database of protected areas in management categories I-VI produced by IUCN-World Conservation Union and WCMC (WCMC 1999). |
| Grassland bird populations | Long-term trend data on breeding birds of North America found along more than 3,500 survey routes over approximately 30 years beginning in 1966, now reported by the U.S. Geological Survey (USGS) (Sauer et al 1997 and 1999). |
| Large grassland herbivores | Long-term population trend data from the Serengeti (Campbell and Borner 1995). |
| Key areas for threatened birds in the Neotropics | Dataset for Latin America with extensive documentation, identifying key areas of threatened species through fieldwork and expert judgment, presented by Birdlife International (Wege and Long 1995). |
| Fragmentation and road densities | Spatial, electronic database of road networks worldwide from Digital Chart of the World (DCW) (ESRI 1993); fragmentation index developed by the World Wildlife Fund (Dinerstein et al. 1995; Ricketts et al 1997) presented in chapter on grassland extent and change. |
| Non-Native species | Dataset for North America aggregating county-level statistics on non-native species to ecoregions, compiled by WWF-US (Ricketts et al. 1997). County lists do not distinguish invasive or harmful introductions from those that are benign or beneficial. |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
♦ Worldwide, almost half of 234 Centers of Plant Diversity (CPDs) include grassland habitat. These CPDs, found in most regions of the world, represent areas with high grassland diversity and where conservation practices could protect a large number of grassland species. ♦ Approximately 23 of 217 Endemic Bird Areas (EBAs) include grassland as the key habitat type; 3 of these 23 grassland EBAs rank highest for biological importance: the Peruvian Andes, Central Chile, and Southern Patagonia. ♦ Of 136 terrestrial ecoregions identified as outstanding examples of the world’s diverse ecosystems, 35 are grasslands, supporting some of the most important grassland biodiversity in the world today. ♦ Less than 16 percent of approximately 4,500 relatively large protected areas are at least 50 percent grassland; protected grasslands cover approximately 4 million km2 or 3 percent of the total land area, just 7.6 percent of the total grassland area. ♦ The highest densities of 28 breeding grassland bird species of North America are found primarily in three states (North Dakota, South Dakota, and Montana) and two provinces (Saskatchewan and Alberta). Population trend data for a nearly 30-year period show a constant decrease in the numbers of these species. ♦ Regional data for African herbivores show generally steady long-term population trends within the Serengeti ecosystem. Areas outside the protected area boundaries and with fewer law enforcement activities experienced decreases in densities of already-low wildlife populations. ♦ Of nearly 600 key areas for threatened bird species in the Neotropics, 42 are grasslands; 12 percent of the threatened birds are specific to grasslands. ♦ Road networks have led to high grassland fragmentation in some areas: the Great Plains of the United States are highly fragmented with 70 percent of the grasslands less than 1,000 km2 while in Botswana, 58 percent of grasslands are 10,000 km2 or greater. ♦ The introduction of non-native species can negatively affect grassland ecosystems through species competition and can eventually lead to decreases in biodiversity. Some North American grasslands support 10 percent to 20 percent non-native plant species. |
♦ Comprehensive data on grassland biodiversity are not adequate to evaluate global grassland condition; we need to expand efforts to systematically collect data on biodiversity for all grassland types and for all flora and fauna, including both macro and micro-soil fauna. ♦ The U.S. Geological Survey supports one of the best programs for collecting status and trends data on grassland birds. Although such expansive programs are not currently feasible in all parts of the world, similar local and regional data collection efforts can be initiated and supported on a gradual basis. ♦ Data on road networks can provide information on the extent of fragmentation and the potential degradation of grassland ecosystems. The current datasets generally do not reflect road building over the last decade. Systematic, consistent coverage with regular updates of electronic, spatial data on road location, size, and use could help us better measure the effects of ecosystem fragmentation. ♦ Rapid expansion of invasive species in grassland ecosystems calls for comprehensive, long-term studies and collection of spatial data on invasive plant and animal species. |
| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Potential carbon stored in grasslands and other terrestrial ecosystems | |
| Estimates for storage in above and below-ground live vegetation | Above- and below-ground vegetation carbon storage estimates (Olson et al. 1983) as modified by USGS/EDC (1999). |
| Estimates for storage in soil | Soil carbon storage estimates based on the International Soil Reference and Information Centre (ISRIC) and World Inventory of Soil Emission Potentials (WISE) global data set of derived soil properties developed by Batjes (1996)and Batjes and Bridges (1994); FAO digital soil map of the world (FAO 1995). |
| Trends and modifications in storage capacity | Various studies reporting on loss of organic carbon or on a reduction in carbon storage potential based on current practices. |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
| ♦ Grasslands store
approximately 34 percent of the global stock of
carbon in terrestrial ecosystems while forests store approximately 39
percent and agroecosystems approximately 17 percent. ♦ Unlike tropical forests, where vegetation is the primary source of carbon storage, most of the grassland carbon stocks are in the soil. ♦ Cultivation and urbanization of grasslands, and other modifications of grasslands through desertification and livestock grazing can be a significant source of carbon emissions. ♦ Biomass burning, especially from tropical savannas, contributes over 40 percent of gross global carbon dioxide emissions. ♦ Some exotic grassland plant species may decrease total carbon storage because they have less extensive below-ground root networks for storing organic matter than native grassland plants. |
♦ Estimates of carbon storage in
terrestrial ecosystems worldwide vary
widely; we need continued updating of models to refine estimates of
carbon storage in grassland vegetation and soils. ♦ Carbon storage estimates need to reflect the influence of different vegetation and soil types and conditions and management practices. ♦ Soil greatly affects the storage potential of grasslands; comprehensive soil studies are needed to improve the accuracy of estimates of that potential. |
| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Tourist numbers and tourism receipts | Annual country-level data compiled by the World Tourism Organization (WTO) and presented by the World Bank (1999). |
| Safari hunting and animal trophies | Data published by IUCN-World Conservation Union for selected African countries and variable time periods (Leader-Williams et al. 1996). |
| Wildlife exploitation index | Measure of wildlife exploitation in North America combining data on effects of hunting and poaching, unsustainable extraction of wildlife as commercial products, and harassment and displacement of wildlife by commercial and recreational users, published by WWF (Ricketts 1997). |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
| ♦ In many countries
with extensive grassland and for which tourism data
are available, the number of international tourists and the
international inbound tourism receipts increased over the 10-year
period from 1985–87 to 1995–97. ♦ The economic contribution of grasslands through recreation and tourism, especially safari tours and hunting, can be high. While providing revenues, grassland tourism also can lead to ecosystem degradation. ♦ Excessive human use and wildlife poaching could decrease the capacity of grasslands to maintain tourism services. |
♦ Data specific to revenues from grassland tourism are rare; we need more systematic collection and reporting of data on grassland tourism revenues. ♦ To adequately monitor the use and effects of tourism and recreation on grassland ecosystems, we need to systematically collect data on multiple aspects of human use of grassland parks and reserves. |