The biodiversity of species and their rates of extinction, distribution, and protection.

Recent studies clarify where the most vulnerable species live, where and how humanity changes the planet, and how this drives extinctions. We assess key statistics about species, their distribution, and their status. Most are undescribed. Those we know best have large geographical ranges and are often common within them. Most known species have small ranges. The numbers of small-ranged species are increasing quickly, even in well-known taxa. They are geographically concentrated and are disproportionately likely to be threatened or already extinct. Current rates of extinction are about 1000 times the likely background rate of extinction. Future rates depend on many factors and are poised to increase. Although there has been rapid progress in developing protected areas, such efforts are not ecologically representative, nor do they optimally protect biodiversity.

Achieving the convention on biological diversity's goals for plant conservation.

Identifying which areas capture how many species is the first question in conservation planning. The Convention on Biological Diversity (CBD) aspires to formal protection of at least 17% of the terrestrial world and, through the Global Strategy for Plant Conservation, 60% of plant species. Are these targets of protecting area and species compatible? We show that 67% of plant species live entirely within regions that comprise 17% of the land surface. Moreover, these regions include most terrestrial vertebrates with small geographical ranges. However, the connections between the CBD targets of protecting area and species are complex. Achieving both targets will be difficult because regions with the most plant species have only slightly more land protected than do those with fewer.

Conserving large populations of lions - the argument for fences has holes.

Packer et al. reported that fenced lion populations attain densities closer to carrying capacity than unfenced populations. However, fenced populations are often maintained above carrying capacity, and most are small. Many more lions are conserved per dollar invested in unfenced ecosystems, which avoid the ecological and economic costs of fencing.

Tropical rainforests: diversity begets diversity.

Tropical rainforests exhibit an extraordinarily high level of biological diversity. A new study shows that the patterns of seedling survival surrounding parent trees are responsible in large part for this amazing diversity.

The lonely earth.

PIP: Biologists have spent time calculating extinction rates and devising conservation programs to determine and trace the rate of wildlife disappearance. Several researchers have resorted to bone hunting in estimating and documenting waves of extinction. However, this method is not feasible in estimating the disappearance of all species. Other researchers have calculated the rate of species extinction based on their findings. Although extinction is a natural part of life, the question remains as to whether the rate is unusual. One study revealed that species tend to last between 1 and 10 million years before they disappear; however, the rate of extinction of these animals and plants is now becoming an annual event. Furthermore, naturalists have documented kilodeath ¿black spots¿ throughout the world, ranging from deserts to rainforests, rivers, and freshwater lakes. Overall, the implication of the disappearance of these species should influence governments in developing and implementing policies that would ensure the protection of wildlife.^ieng

Ecology: engineered food webs.

An important new study shows that, in a food web, the strengths and arrangement of the interactions between species are determining factors of stability of the system.

Forest losses predict bird extinctions in eastern North America.

Claims that there will be a massive loss of species as tropical forests are cleared are based on the relationship between habitat area and the number of species. Few studies calibrate extinction with habitat reduction. Critics raise doubts about this calibration, noting that there has been extensive clearing of the eastern North American forest, yet only 4 of its approximately 200 bird species have gone extinct. We analyze the distribution of bird species and the timing and extent of forest loss. The forest losses were not concurrent across the region. Based on the maximum extent of forest losses, our calculations predict fewer extinctions than the number observed. At most, there are 28 species of birds restricted to the region. Only these species would be at risk even if all the forests were cleared. Far from providing comfort to those who argue that the current rapid rate of tropical deforestation might cause fewer extinctions than often claimed, our results suggest that the losses may be worse. In contrast to eastern North America, small regions of tropical forest often hold hundreds of endemic bird species.

Biodiversity. Managing nature when there are no 'ill winds'.

Interspecific interactions affect biodiversity, but in unpredictable ways that change over time and space. There is little evidence for the 'ill wind that blows no good' to any species. So how can we manage nature?

The future of biodiversity.

Recent extinction rates are 100 to 1000 times their pre-human levels in well-known, but taxonomically diverse groups from widely different environments. If all species currently deemed "threatened" become extinct in the next century, then future extinction rates will be 10 times recent rates. Some threatened species will survive the century, but many species not now threatened will succumb. Regions rich in species found only within them (endemics) dominate the global patterns of extinction. Although new technology provides details of habitat losses, estimates of future extinctions are hampered by our limited knowledge of which areas are rich in endemics.

Extinction rates. Modern extinctions in the kilo-death range.

For some groups of species, extinction rates are orders of magnitude higher than expected background rates--many species now last nearer a fateful second than their destined hour.

Biological diversity. Species: would any of them be missed?

Contrary to the view taken by some, individual species matter: they are valuable for their contribution to the stability of the ecosystems they inhabit.

Times to extinction for small populations of large birds.

A major practical problem in conservation biology is to predict the survival times-"lifetimes"-for small populations under alternative proposed management regimes. Examples in the United States include the 'Alala (Hawaiian Crow; Corvus hawaiiensis) and Northern Spotted Owl (Strix occidentalis caurina). To guide such decisions, we analyze counts of all crow, owl, and hawk species in the most complete available data set: counts of bird breeding pairs on 14 European islands censused for 29-66 consecutive years. The data set yielded 129 records for analysis. We define the population ceiling as the highest number of breeding pairs observed from colonization to extinction, within a consecutive series of counts for a given species on a given island. The resulting distributions of population lifetimes as a function of population size prove to be highly skewed: most small populations disappear quickly, but a few last for a long time. Median (i.e., 50th percentile) lifetimes are calculated as only 1-5 yr for hawk, owl, and crow populations with ceilings of one or two breeding pairs. As expected if demographic accidents are the main cause of extinction for small populations, lifetimes rise by a factor of 3-4 for each additional pair up to three pairs. They rise more slowly thereafter. These observations suggest that lifetimes of the 'Alala (now reduced to about three pairs in the wild), and of populations of Northern Spotted Owl in the smallest forest fragments, will be short unless active management is implemented.