PerspectiveEcology

Are Global Conservation Efforts Successful?

See allHide authors and affiliations

Science  25 Aug 2006:
Vol. 313, Issue 5790, pp. 1051-1052
DOI: 10.1126/science.1131302

Human actions affect ecosystems worldwide, leading to irreversible losses in biodiversity. These changes were faster in the past 50 years than at any time in human history, and this acceleration is projected to continue (1), despite diverse efforts to prevent these losses. Do these efforts make any measurable difference in the global state of biodiversity? The combined results of the 2006 World Conservation Union (IUCN) Red List of Threatened Species (2) and of a study by Butchart et al. (3) provide the first opportunity to assess the impact of global conservation investment on biodiversity.

Measuring global conservation impact is not simple. Biodiversity is not easily quantified (4), and resources for monitoring it fall woefully short (5). Moreover, innumerable conservation activities take place worldwide, with approaches as diverse as single-species management, ecosystem restoration, environmental education, and political lobbying. Their scales range from local to global, with various degrees of coordination, replication, and synergy among them. Overall conservation impact can thus not be measured as the summed impacts of individual actions.

One useful approach is to compare the observed change in global biodiversity with the predicted change in the absence of such efforts. In the best-case scenario, conservation action would maintain biodiversity at a stable level, because global biodiversity does not increase on a time-scale relevant to human enterprise. More realistically, conservation action might be considered successful if it slows down the human-induced rate of global biodiversity decline.

This approach can now be applied to birds, the best-studied vertebrate group. The 2006 IUCN Red List reports 135 bird species that have become extinct since 1500 (2). The numbers of extinctions per century increased steadily to 49 in the 19th century, but then appear to decline to 43 in the period from 1901 to 2006 (see the first figure). This could be mistaken as evidence that the human impact on birds has weakened. However, recent extinctions are underestimated because of the time lag between the disappearance of a species from the wild and the confirmation of its extinction.

Bird extinction trends.

Estimated numbers of bird extinctions in the past five centuries, and of extinctions prevented through conservation action. See the Supporting Online Material for information on the species in each class. (Inset) The Atitlán grebe (Podilymbus gigas) was driven to extinction in 1986 in its native Lake Atitlán, Guatemala (9).

IMAGE: ALISTAIR ROBERTSON/BIRDLIFE INTERNATIONAL

For a species to be listed as “Extinct” on the IUCN Red List, exhaustive surveys must have been undertaken in all known or likely habitat throughout its historic range, at appropriate times, and over a time frame appropriate to its life cycle and life form (6). To avoid the “Romeo error” (7) of giving up on a species when it is not yet too late, conservationists are reluctant to designate species as “Extinct” if there is any chance that they may still persist (8). A framework has been developed to examine relevant evidence and judge as objectively as possible which species may already be extinct (8). Fifteen birds are listed as “Critically Endangered (Possibly Extinct)” in the 2006 IUCN Red List (2, 9), revealing an uninterrupted upward trend of extinction rates (see the first figure).

Butchart and colleagues (3) add the missing piece required to evaluate conservation impact. Using data on population sizes, population trends, threatening processes, and conservation actions, they identify at least 26 bird species surviving in the wild that would have very probably gone extinct if conservation programs for them had not been undertaken. Four additional species are classified as “Extinct in the Wild” and one as “Critically Endangered (Possibly Extinct in the Wild),” only surviving (or possibly only surviving) in captive breeding programs (2, 8). These 31 species represent the gain in extant bird species attributable to conservation action, providing a measure of the success of global conservation in preventing bird extinctions (see the second figure). In the absence of conservation, the rates of bird extinctions would thus have increased dramatically into the present (see the first figure).

This is the first time that global conservation impact has been quantified with a direct biodiversity measure, rather than with indicators of conservation effort such as area protected (10) or money invested (11). Nonetheless, this is a crude appraisal that uses a narrow measure of biodiversity and inevitably underestimates the overall impact of conservation efforts. Conservation efforts aim at much more than avoiding the ultimate extinction of species, including preventing species from becoming threatened in the first place and ensuring the health of the ecosystem processes that support biodiversity. Measures of conservation impact with finer temporal and ecological resolution are urgently needed to assess progress toward the United Nations 2010 Biodiversity Target of reducing the rate of biodiversity loss (5).

Conservation impact.

Estimated impact of global conservation action on preventing extinction, compared to the impact of human activities on overall bird species richness. Total numbers of species are based on the taxonomy followed in (2, 9). (Inset) Extinction of the Seychelles magpie-robin (Copsychus sechellarum) was prevented through a conservation program that included translocations, habitat management, and eradication of invasive species (9).

IMAGE: CATH MULLEN/BIRDLIFE INTERNATIONAL

Moreover, there is no room for complacency. None of the 31 bird species can be declared as saved; most still face a very high risk of extinction and depend on continued conservation efforts (2, 3). Preventing each of these extinctions has typically required a mix of conservation interventions, including actions that might benefit other threatened species in the same localities (such as habitat protection and predator control; 22 species) and species-specific actions (such as captive breeding and translocations; 21 species).

A major increase in global conservation resources would be required to extend such dedicated efforts into each of the thousands of threatened species (2). Just among birds, 1210 species are listed as threatened (2, 9). The populations of 217 highly threatened bird species are confined to single sites (12) and could be lost very rapidly. The number of bird extinctions is expected to increase rapidly in the near future, unless considerable action is taken.

Nonetheless, it is encouraging that bird conservation actions worldwide are making a noticeable dent in the bleak scenario of global biodiversity loss. In many cases, this may simply amount to buying a little time, but while a species is extant we can still have hope for its recovery in the future. Extinction, on the other hand, is forever.

Supporting Online Material

www.sciencemag.org/cgi/content/full/313/5790/1051/DC1 Tables S1 to S5 References

References and Notes

  1. 1.
  2. 2.
  3. 3.
  4. 4.
  5. 5.
  6. 6.
  7. 7.
  8. 8.
  9. 9.
  10. 10.
  11. 11.
  12. 12.
  13. 13.
View Abstract

Navigate This Article