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


Science 30 May 2014:
Vol. 344 no. 6187
DOI: 10.1126/science.1246752
  • Review

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

  1. S. L. Pimm1,*,
  2. C. N. Jenkins2,
  3. R. Abell3,,
  4. T. M. Brooks4,
  5. J. L. Gittleman5,
  6. L. N. Joppa6,
  7. P. H. Raven7,
  8. C. M. Roberts8,
  9. J. O. Sexton9

+ Author Affiliations

  1. 1Nicholas School of the Environment, Duke University, Box 90328, Durham, NC 27708, USA.

  2. 2Instituto de Pesquisas Ecológicas, Rodovia Dom Pedro I, km 47, Caixa Postal 47, Nazaré Paulista SP, 12960-000, Brazil.

  3. 3Post Office Box 402 Haverford, PA 19041, USA.

  4. 4International Union for Conservation of Nature, IUCN, 28 Rue Mauverney, CH-1196 Gland, Switzerland.

  5. 5Odum School of Ecology, University of Georgia, Athens, GA 30602, USA.

  6. 6Microsoft Research, 21 Station Road, Cambridge, CB1 2FB, UK.

  7. 7Missouri Botanical Garden, Post Office Box 299, St. Louis, MO 63166–0299, USA.

  8. 8Environment Department, University of York, York, YO10 5DD, UK.

  9. 9Global Land Cover Facility, Department of Geographical Sciences, University of Maryland, College Park, MD, 20742, USA.
  1. *Corresponding author. E-mail:


A principal function of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) is to “perform regular and timely assessments of knowledge on biodiversity.” In December 2013, its second plenary session approved a program to begin a global assessment in 2015. The Convention on Biological Diversity (CBD) and five other biodiversity-related conventions have adopted IPBES as their science-policy interface, so these assessments will be important in evaluating progress toward the CBD’s Aichi Targets of the Strategic Plan for Biodiversity 2011–2020. As a contribution toward such assessment, we review the biodiversity of eukaryote species and their extinction rates, distributions, and protection. We document what we know, how it likely differs from what we do not, and how these differences affect biodiversity statistics. Interestingly, several targets explicitly mention “known species”—a strong, if implicit, statement of incomplete knowledge. We start by asking how many species are known and how many remain undescribed. We then consider by how much human actions inflate extinction rates. Much depends on where species are, because different biomes contain different numbers of species of different susceptibilities. Biomes also suffer different levels of damage and have unequal levels of protection. How extinction rates will change depends on how and where threats expand and whether greater protection counters them.


Different visualizations of species biodiversity. (A) The distributions of 9927 bird species. (B) The 4964 species with smaller than the median geographical range size. (C) The 1308 species assessed as threatened with a high risk of extinction by BirdLife International for the Red List of Threatened Species of the International Union for Conservation of Nature. (D) The 1080 threatened species with less than the median range size. (D) provides a strong geographical focus on where local conservation actions can have the greatest global impact. Additional biodiversity maps are available at


Recent studies have clarified where the most vulnerable species live, where and how humanity changes the planet, and how this drives extinctions. These data are increasingly accessible, bringing greater transparency to science and governance. Taxonomic catalogs of plants, terrestrial vertebrates, freshwater fish, and some marine taxa are sufficient to assess their status and the limitations of our knowledge. Most species are undescribed, however. The species we know best have large geographical ranges and are often common within them. Most known species have small ranges, however, and such species are typically newer discoveries. The numbers of known species with very small ranges are increasing quickly, even in well-known taxa. They are geographically concentrated and are disproportionately likely to be threatened or already extinct. We expect unknown species to share these characteristics. Current rates of extinction are about 1000 times the background rate of extinction. These are higher than previously estimated and likely still underestimated. Future rates will depend on many factors and are poised to increase. Finally, although there has been rapid progress in developing protected areas, such efforts are not ecologically representative, nor do they optimally protect biodiversity.


Progress on assessing biodiversity will emerge from continued expansion of the many recently created online databases, combining them with new global data sources on changing land and ocean use and with increasingly crowdsourced data on species’ distributions. Examples of practical conservation that follow from using combined data in Colombia and Brazil can be found at and

  • † Authors after the second are in alphabetical order.




Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.