“An inordinate fondness for beetles” is what the celebrated biologist J.B.S. Haldane apocryphally quipped when asked his opinion of God.

Beetles comprise just under a third of the 1.2 million species described so far [], and a recent paper has estimated that there are about 7-10 million species on the planet. In other words, we have yet to describe about 86% of the species on continents, and about 91% of oceanic diversity. These estimates are limited to one of three major domains of life, the eukaryotes (which include plants. animals, fungi, and some microbes such as amoeba), because biologists don’t yet have a good way of cataloguing the other domains of life — the true bacteria and the archaea — which comprise single-celled organisms that are hard to see and even harder to count []. What we do know is that much of biodiversity (even of beetles) remains unknown.

What is biodiversity?

Biodiversity does not simply translate into species numbers; it also includes genetic and ecological diversity. At the smallest scale, genetic diversity within species includes important variations in such traits as resistance to different parasites. Species diversity refers to the variation within populations and to the differences between species. At the largest scale, there are many different habitats and ecosystems, each of which cycles water and key elements differently. One of the most important aspects of biodiversity is the inextricable interrelatedness of all the parts, be they genes, species, or populations.

What does biodiversity do?

Removing one species is enough to reduce some of nature’s cathedrals to rubble. For instance, who would have guessed that more fur coats could result in less seafood? This is precisely what happened in a famous example off the west coast of North America. Sea otters were severely hunted for their fur for about 150 years, until they were close to extinction in the early 20th century. As a result, the otters’ favorite prey, sea urchins, reproduced in droves, and consumed most of the kelp that sustain an entire community of fish, crabs and shellfish []. The sea otter is an example of what ecologists call a keystone species, because removing that one species is sufficient to cause the collapse of an entire ecosystem.

In addition to the obvious benefits of food, shelter and medicines, healthy ecosystems provide services that most human organizations would be hard-pressed to produce.  Clean water, clean air, and fertile soil are lost when we disrupt the intricate combinations of organisms in ecosystems. One of the most compelling instances of an ecosystem service is pollination. Insects and animals sustain at least a third of the world’s crops free of charge through pollination []. Farmers who have lost these natural pollinators have to resort to the fiddly and expensive business of paying people to dab bits of pollen onto flowers with brushes made of chicken feathers [].

What threatens biodiversity?

It is a truth not universally acknowledged that humans would go extinct without biodiversity. Conversely, much of biodiversity is threatened thanks to our actions. A major threat to biodiversity is habitat loss. For instance, many natural pollinators cannot exist in vast, continuous stretches of the same crop, so removing the wild habitat to maximize land on which crops are planted can lead to a decrease in organisms that pollinate our plants. Man-made changes to the compositions of ecosystems can disturb them in unforeseen and indirect ways. For instance, the culling of coyotes in southern California can lead to the decimation of songbirds, because racoons, usually kept in check by coyotes, multiply and devour songbird eggs. Similarly, introduced species can bring diseases or dominate communities, causing many native species to go extinct. Overexploitation is another handy way to ensure that we won’t have much left to live on in the future. About 90% of the world’s predatory fish, like tuna and salmon, are gone due to human exploitation []. Pollution is another clear threat to biodiversity. Our carelessly discarded detritus can do damage thousands of miles away, as seen in this picture of a collection of plastics in the carcass of an albatross chick [].

Photograph by Chris Jordan

Climate change is a major threat to entire ecosystems. The Arctic has lost over a quarter of its floating sea ice in the last 20 years. As the reflective ice and snow melt, they are replaced by dark water that absorbs more heat. This increased heat alters the temperature and salinity of the ocean, changing ocean circulation and species composition, while also changing temperatures inland and destroying tundra. In addition, many species cannot adapt fast enough to changing temperatures and seasons []. We know that this could be a threat to species because a very recent paper showed that most of the Ice Age mammals went extinct because of climate change and human activity [].

“Biodiversity and Climate Change”. From the Convention on Biological Diversity.

To lose a few species may be regarded as unfortunate. To lose 27,000 species a year looks like carelessness[]. Many organizations are attempting to stanch the bleeding of biodiversity by identifying “biodiversity hotspots”, areas with unusually high concentrations of unique diversity, as conservation priorities, and are working with local communities so that conservation benefits people directly and not just in the long run. Ultimately, there are both pragmatic and moral reasons for conserving biodiversity. If humans wish to continue living a high quality of life with decent air, food, water, shelter, and medical aid, then it would behoove us to protect the biodiversity upon which so much of our lives depend.

Wenfei Tong is a PhD student in the Department of Organismic and Evolutionary Biology at Harvard University.


[] “EOL: Coleoptera – Encyclopedia of Life.” [Online]. Available: http://eol.org/pages/345/overview.

[] Mora C, Tittensor DP, Adl S, Simpson AGB, Worm B, 2011 How Many Species Are There on Earth and in the Ocean? PLoS Biol 9(8): e1001127. doi:10.1371/journal.pbio.1001127

[] “food web.” [Online]. Available: http://cbc.amnh.org/crisis/foodweb.html. [Accessed: 03-Nov-2011].

[]  “Biodiversity: Pollinators.” [Online]. Available: http://www.fao.org/biodiversity/components/pollinators/en/.

[] “Biodiversity and the Ecosystem Approach in Agriculture, Forestry and Fisheries.” [Online]. Available: http://www.fao.org/DOCREP/005/Y4586E/y4586e11.htm.

[]  “Overfishing – A global environmental problem, threat to our oceans and disaster.” [Online]. Available: http://overfishing.org/pages/why_is_overfishing_a_problem.php.

[] “The Pacific’s plastic shame | Environment | guardian.co.uk.” [Online]. Available: http://www.guardian.co.uk/environment/gallery/2009/nov/03/albatross-plastic-poison-pacific?intcmp=239#/?picture=355118656&index=0.

[] “Climate Change Affects Biodiversity — Global Issues.” [Online]. Available: http://www.globalissues.org/article/172/climate-change-affects-biodiversity.

[] E. D. Lorenzen et al., “Species-specific responses of Late Quaternary megafauna to climate and humans,” Nature, vol. advance online publication, Nov. 2011.

[] “Evolution: Library: The Current Mass Extinction.” [Online]. Available: http://www.pbs.org/wgbh/evolution/library/03/2/l_032_04.html.

Links of Interest:

Biodiversity Hotspots, Conservation International http://www.biodiversityhotspots.org/xp/hotspots/Pages/default.aspx

International Union for Conservation of Nature http://www.iucn.org/

International Year of Biodiversity http://www.cbd.int/2010/welcome/

Biodiversity Heritage Library http://www.biodiversitylibrary.org/

Biodiversity Conservation http://www.biodiversityconservationsource.com/

Why Is Biodiversity Important? Who Cares? (Global Issues) http://www.globalissues.org/article/170/why-is-biodiversity-important-who-cares

Biodiversity (The Encyclopedia of Earth) http://www.eoearth.org/article/Biodiversity?topic=49480

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