Yosemite National Park
Protecting and Restoring Biodiversity

We must make every effort to preserve, conserve, and manage biodiversity. Protected areas, from large wilderness reserves to small sites for particular species, and reserves for controlled uses, will all be part of this process. Such systems of protected areas must be managed to take account of a range of ecological and human-induced changes. This is no small task; yet humans must be equal to this challenge, or risk becoming irrelevant.

- Peter Bridgewater, National Parks and Wildlife Service, Australia

01/04/2006 Format for printing

We wish to learn:

  • What is the current extent of protected area?
  • How does the level of protection vary among protected areas?
  • How can we best determine where new protected areas are needed?
  • How might we design nature reserves to maximize their effectiveness?
Jump to: [Extent of Protected Areas] [Placement of Protected Lands] [Design of Nature Reserves] [Summary] [Suggested Readings]


Many species and ecosystems will disappear over the next century. However, starting with recognizing the problem, and then identifying management objectives, much can be done to alleviate this trend. A sound strategy would emphasize improving our management of existing protected land, and strategically adding new protected areas. Ecological systems have considerable potential to recover if appropriate restoration measures are taken. Ultimately we wish to manage populations and ecosystems sustainably, so that they may be utilized and enjoyed by future generations. These are the goals of science-based management. 

Extent of Protected Areas

The World Resources Institute estimates that there are 8,163 protected areas worldwide, managed for various objectives ranging from strict nature protection to controlled harvesting. They cover 750 million hectares (1 hectare = 2.5 acres) of marine and terrestrial ecosystems, which is about 1.5% of the Earth's surface, and 5.1% of national land area. In many developing countries, the existence of protected areas creates conflicts for local people, who may depend upon that area for their subsistence. Often, enforcement of laws protecting parks is minimal.

The map below, created by the World Resources Institute, reflects the global variation in land protection.

Protection of biodiversity requires a network of reserves, including some large enough to protect many species and wide-ranging species, located where appropriate habitat exists, and protected from exploitation. Due to growing awareness, the amount of protected land is increasing. However, it is unlikely to ever exceed 6% of the Earth’s land surface, and even that amount may be optimistic. Nonetheless, parks and sanctuaries can be very effective, protecting a significant fraction of an area’s wildlife. Protected lands receive different levels of protection -- Some lands are highly protected as nature reserves, others as scenic areas, and still others provide for multiple use, including resource extraction.

IUCN Protected Area Categories Based on Management Purpose:

Category I. Strict Protection: Sometimes called strict nature reserve/wilderness areas. Protected areas managed mainly for science or wilderness protection. Generally smaller areas where the preservation of important natural values with minimum human disturbance are emphasized.

Category II. Ecosystem Conservation and Tourism: Sometimes called national parks. Generally larger areas with a range of outstanding features and ecosystems that people may visit for education, recreation, and inspiration as long as they do not threaten the area's values.

Category III. Conservation of Natural Features: Sometimes called natural monuments. Similar to National Parks, but usually smaller areas protecting a single spectacular natural feature or historic site.

Category IV. Conservation Through Active Management: Sometimes called habitat and wildlife (species) management areas. Areas managed to protect and utilize wildlife species.

Category V. Landscape/Seascape Conservation and Recreation: Sometimes called protected landscapes/seascapes.

Category VI. Sustainable Use of Natural Ecosystems: Sometimes called managed resource protected areas. Protected areas managed mainly for the sustainable use of natural ecosystems.

The number of protected areas and their distribution among biogeographical regions is given in Table 1. Table 2 documents that new protected areas are being established around the world. Table 3 shows that protection of even a relatively small fraction of a nation's land area can be effective in protecting a substantial fraction of that nation's biological diversity.

Table 1. Number of Protected Areas and the Total Area of Various Biogeographical Regions They Cover

Scientific Reserve National Park National Monument Wildlife Reserve Protected Landscape Total
Region No.
Nearctic 5 11,600 142 1,155,500 32 64,200 249 380,700 40 113,600 478 1,725,600
Palearctic 313 273,100 204 112,300 24 2,000 649 172,800 494 171,700 1684 731,900
Afrotropical 23 17,600 152 574,300 1 <100 260 268,700 8 300 444 860,900
Indomalayan 63 27,900 158 111,300 5 300 411 180,400 39 2,900 676 322,800
Oceanian 17 25,900 10 3,300 0 0 24 19,600 1 <100 52 48,900
Austrailian 58 23,100 248 192,600 0 0 277 137,500 40 3,700 623 356,900
Antartic 29 6,500 11 21,000 5 200 85 3,500 0 0 130 31,200
Neotropical 55 63,900 224 423,900 22 2,900 126 244,900 31 32,500 458 768,100
Total 563 449,600 1,149 2,549,200 89 69,600 2,091 1,408,100 653 324,800 4,545 4,846,300
Source: Protected Areas Data Unit, World Conservation Monitoring Centre, May 1989. Table from Reid and Miller 1989.


Table 2. Rate at which new protected areas have been established throughout the world
Date Established Number of areas Total area protected (km^2)
Unknown 711 194,395
Pre-1900 37 51,455
1900-1909 52 131,385
1910-1919 68 76,983
1920-1929 92 172,474
1930-1939 251 275,381
1940-1949 119 97,107
1950-1959 319 229,025
1960-1969 573 537,924
1970-1979 1,317 2,029,302
1980-1989 781 1,068,572
From Reid and Miller 1989.


Table 3. Percent of a country's bird species found within protected areas for selected African nations.
Country Percent of national land area protected Number of bird species Percent of bird species found in protected areas
Cameroon 3.6 848 76.5
Cote d'Ivoire 6.2 683 83.2
Ghana 5.1 721 77.4
Kenya 5.4 1064 85.3
Malawi 11.3 624 77.7
Nigeria 1.1 831 86.5
Somalia 0.5 639 47.3
Tanzania 12.0 1016 82.0
Uganda 6.7 989 89.0
Zaire 3.9 1086 89.0
Zambia 8.6 728 87.5
Zimbabwe 7.1 635 91.5
From Sayer and Stuart 1988.

Placement of Protected Lands

Where to concentrate one's efforts is a critical issue facing conservation groups and government agencies. The uniqueness of an ecosystem, the number of species, especially endemic species (see GCI speciation lecture) it supports, and the imminence of the threats to its survival all play a role in the targeting of conservation activities. The World Wildlife Fund has identified 25 ecosystems around the world for highest priority (see locations on map below).

The size and placement of existing protected areas around the world are determined by many factors, and not necessarily primarily by conservation needs. Many are located in remote and unproductive lands, or in areas of great scenic beauty, or as a result of a conservation-minded national leader, philanthropist, or member of royalty. Some are in logged-over areas, and are only beginning to recover to their original splendor. A map of U.S. wilderness areas is a useful reminder that only a few percent of rivers and total land area, at most, are protected. In the U.S., there is more protected land in the West, partly due to its scenic beauty, but partly because much of this area is less productive.


At least until recently, the system of protected areas has been almost entirely haphazard. Gap analysis is a new approach based on mapping of vegetation, animals (usually terrestrial vertebrates) and land ownership in order to identify gaps in the network of parks, reserves, and public lands that hopefully protect the biodiversity they contain.

Gap analysis relies on three primary data layers. These are:

1. The distribution of actual vegetation types, delineated from satellite imagery:

A. Landsat TM Satellite Image.
B. Resulting Vegetation Map.

2. The distribution of terrestrial vertebrates, predicted from the vegetation distribution by associating individual species with the vegetation that characterizes their habitat.

3. The distribution of land ownership:

The process can be as simple as placing layers of transparent mylar over a base map, such as a topo map, and tracing the information onto separate layers of transparencies. The first gap analysis looked at the distribution of three species of endangered Hawaiian honeycreepers (forest birds) on the island of Hawaii. It was possible to see the distribution of each bird species, and also locations where all three species coincided. Logically, these areas would be conservation priorities. Although the island had a number of nature reserves, none overlapped the birds’ distributions. These maps determined the site for a new reserve.

Extending this approach to a large scale depends on computer mapping of satellite images. Landsat TM (thematic mapper) or other remotely sensed imagery may be used to construct vegetation maps. Landsat TM receives seven spectral bands of reflected infrared light, in individual cells or pixels of 30m x 30m. Image classification uses those spectral data to develop a map of vegetation classes (see maps A and B above), which is compared to ground measurements to improve accuracy. The resulting vegetation map is geo-referenced, meaning that every location has a latitude and longitude or some other X-Y grid location.

Specialized computer software, along with these spatial data and other information, make up a Geographic Information System (GIS)

Using these data layers and a GIS, one can ask:

  • What fraction of threatened species occurs within existing reserves?
  • What fraction of each major vegetation type falls within existing reserves?
  • Are areas of highest species richness found within existing reserves?
  • Are areas of high endemism found within existing reserves?
This map of the distribution of a desert reptile, the gila monster, shows that its distribution falls mainly outside protected land areas.

Design of Nature Reserves

Many factors influence the design as well as the placement of nature reserves. These include the specific habitat needs of species, the climate/soil/spatial requirements of ecosystems that one wishes to protect, and possible conflicts with human use of the target location. We will focus on some biological issues.

Reserves must be of sufficient size to maintain "large enough" populations of all "important species."

  • What is large enough? This depends on the species of course. But as general rule of thumb, a minimum "viable population" contains at least several hundred reproductive individuals. Several thousand is more desirable. A reserve should be large enough to preserve a viable population of the most wide-ranging species found therein.
  • What are the important species? The answer to this question will vary. (perhaps all species?) But species of conservation concern (rare, endangered), keystone species (see ecological communities lecture), and economically important species should certainly be considered.
Reserves should protect at least several populations, with a metapopulation structure. A metapopulation is a "population of populations," or set of subpopulations that are spatially distinct, but have some migration between them (see Figure 1). Over a time span of a hundred years or more, a single population might experience catastrophic bad luck -- a storm, fire, disease outbreak, etc. The existence of multiple populations, with limited dispersal and genetic exchange, provides insurance for the survival of the population as a whole, while maintaining genetic diversity. 
  • Reserve design can encourage natural migration through the use of corridors and stepping stones for connectivity.
  • Individual plants and animals can be physically transferred if necessary.
Figure 1. Mountain Sheep Metapopulation in Southern California.  Shaded areas indicate mountain ranges with resident populations, arrows indicate movement of populations between mountain ranges.  From RAMAS GIS

Reserves should also minimize edge and fragmentation effects.

  • Round shapes, which minimize edge, should be favored over elongated shapes, which maximize edge.
  • Internal fragmentation of a reserve due to logging, farming, roads, power lines, etc., should be avoided.
  • Small areas can often be aggregated to create larger conservation blocks by including surrounding land, even if some areas are given lower conservation priority. This can create a land mosaic containing areas of varying conservation status, but under integrated management.
  • Entire ecosystems should be incorporated if possible.
Reserves should consciously include the matrix of unprotected land in which they are embedded. Non-protected areas make up >95% of the landscape, so parks and sanctuaries necessarily exist in a matrix of developed land. Species wander outside of parks routinely. Future climate change raises the alarming likelihood that the entire flora and fauna of parks will migrate outside their current sanctuaries, as the climate within the park boundaries becomes unsuitable.

Priorities for reserve management include:

  • Forming partnerships with public (agencies) and private (citizens) land owners.
  • Education of land owners and the general public.
  • Establishment of mechanisms to resolve land-use conflicts.


  • At present, some 8,163 protected areas worldwide cover about 1.5% of the Earth's surface, and 5.1% of national land area.
  • Protected areas are managed for various objectives ranging from strict nature protection to controlled harvesting. The IUCN lists six protected area categories based on management purpose.
  • Gap analysis maps vegetation, animals (usually terrestrial vertebrates) and land ownership in order to identify gaps in the network of parks, reserves, and public lands that are necessary to protect species and ecosystems currently outside the protected areas network.
  • Many factors influence the design as well as the placement of nature reserves, including: sufficient size, metapopulation structure, minimization of edge and fragmentation effects, and a planning process that links reserves to the surrounding matrix of unprotected land.


Suggested Readings

  • Fiedler, P.L. and S.K. Jain, Editors. 1992. Conservation Biology: The Theory and Practice of Nature Conservation Preservation and Management. Chapman and Hall, New York.
  • Soule, M.E. Conservation Biology: the Science of Scarcity and Diversity. Sinauer Press, Sunderland, MA.

  • Primack, R.B. 1997. Essentials of Conservation Biology. Sinauer Associates, Sunderland MA

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