Grassland biodiversity encompasses a wide range of goods useful to humans.
Grasslands have been the seedbeds for the ancestors of major cereal crops, including wheat, rice, rye, barley, sorghum, and millet. They continue to provide the genetic material necessary to breed cultivated varieties that are resistant to crop diseases. Grasslands also provide habitat for plants and animals-soil microfauna and large mammals alike.
Global and regional datasets identify biodiversity in the world’s grasslands. The PAGE analysis reviews these datasets, paying special attention to areas designated as especially important for preserving grassland biodiversity.
The following summarizes key findings of the PAGE study regarding the condition of grassland ecosystems, as well as the quality and availability of data.
Conditions and trends
- 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 square kilometers 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 square kilometers while in Botswana, 58 percent of grasslands are 10,000 squar kilometers 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.
Information status and needs
- 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.
Quality and availability of data
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 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.