Some species are headline grabbers (the honeybee, for instance).  Others may garner far less media coverage (certain tree species for instance).  But the list of disappearing, endangered, or extinct species is growing.  And the causes and implications for humans and the global ecosystems are not fully known.

Some disappearing species, like pollinators (ie: the honeybee) may be leading to other population declines due to mutualism, or the biological concept that two species interact in a way that is beneficial to both species (ie: honeybees derive nectar, plants get pollinated). Other types of biological interactions may also be implicated when one species loses homeostasis, and its numbers either grow too large or decrease too much.  These other interactions include symbiosis, where one species is positively affecting the survival of another (think the small fish that clean shark's teeth), or predation (where one species negatively affects the survival of another).  All three of these interactions are natural and do not lead to species loss when there is a natural balance, or homeostasis.

It is not yet known why the honeybee numbers have been rapidly declining for about three years now (termed colony collapse disorder), and it is not yet fully appreciated what impact this will have on the plants which the honeybee pollinates.   Recent research points to a collection of viruses which may be the culprit for the honeybee disorder, the combination of which may overwhelm their immune systems.  However the exact cause of their death, or the reason for a potential viral assault are not yet known.  Other hypotheses have also been made to explain colony collapse disorder, including farming practices which may affect hive health and the bee's ability to ward off harmful viruses.  This loss of honeybees puts at risk nearly 100 food crops, and effects beyond that are not yet known.

In deer,  elk and other cervids (hooved ruminants), a prion disease called chronic wasting disease (CWD) is decimating their populations across areas of the central US.  A prion disease, like the well known Mad Cow (or creutzfeldt-jakob) disease, is when a misfolded protein leads other proteins to misfold, and this domino-effect leads to neurological damage (for more on prion disease visit: http://www.cdc.gov/ncidod/dvrd/prions/).  It is not yet know how CWD is being transmitted among the deer and elk populations, but it is not thought to be transmissable to humans.

In bats, white nose syndrome has been compared to colony collapse disorder in bees. This disease was first observed by a caver in New York in 2006, who noticed among the normally hibernating bats some dead bats, and some bats with a white substance on their muzzles.  Since then, observations like these have increased and hundreds of thousands of bats have died as a result of what has now been identified as a white fungus.  This fungus has been associated with decreased body fat in the bats (which is required for them to maintain their hibernating state), and odd behavior such as arousing to feed on insects during the day (usually bats feed at dawn and dusk when insects are more prevalent). Several research studies are underway in the northeast to search for a cause and possible cure for this devastating disease.  Bats are an important part of the food chain, in that they serve many roles such as predation of insects and acting as pollinators (more about the importance of bats can be found here: http://www.mcrcc.osmre.gov/PDF/Forums/Bat%20Conservation/1a.pdf).

Its not just animal species which are in decline.  Many species of plants are also experiencing huge losses, including the red pine trees in northwest (more here on red pine: http://plantclinic.cornell.edu/FactSheets/redpine/redpinedecline.htm) and several species of seagrass (15% worldwide threatened, with effect on dependent species).  The causes of plant species decline are myriad and include take-over by invasive species and insect threats (a nice description of one state's invasive species threats can be found here: http://www.maine.gov/doc/mfs/InvasiveThreats.htm).The ecosystem implications for loss of plant species are many, and include a threat to the food system and loss of other species in the food chain.

A 2005 study (Cardillo et al., Science) suggests that species loss may be more exaggerated in larger species (remember Save the Whales, anyone?) simply because of their large body size and low reproductive rates.  However, these also tend to be the species most hunted by the members at the top of the food chain: humans. These also may be the species we hear more about, because of their emotional association as 'charasmatic megafauna'.

One success story of restoring a decimated species can be illustrated with a species of butterfly in the UK.   The blue butterfly was declared extinct about 30 years ago, and subsequent research determined their loss was due to the loss of their food source, the red ants who's hills were destroyed due to urbanization. The observation of their lacking numbers and subsequent research into the causes, lead to intervention.  Blue butterflies from Sweden began to be introduced to the UK in the 1980's, and by this year, their numbers appear to be approaching those before the loss.  However, there are many other species of butterfly recorded in decline in the UK, with the worst numbers reported last year since recording begain in the 70's.

 The Red List is an international list of threatened species (found at: http://www.iucnredlist.org/).  This list has been in existance for over 40 years, and separates species by category such as conservation status (ie: extinct vs. extinct in the wild, for example).  The list also shows species prevalence across geographic areas.  One signal for a geographic area's environmental perturbations (and potential for mass loss of species), may be the health and numbers of a so-called signal species, like amphibians.  Loss of amphibians, like frogs, are thought to be an early signal of the health of an ecosystem.  Amphibians may respond earlier to ecosystem disturbances due to their watery niche and their absorbant skins.

 Endangered and extinct species have been part of our education since Kindegarten, although it can be difficult to maintain knowledge and interest.  These examples illustrate how threatened species are still a major problem, because the numbers of species in decline are increasing,  and the causes are not always clear but the implications for human and environmental health are clear. As the blue butterfly example shows us, observation, education of the public, research, and action are the steps to be taken to combat species loss.

Further Reading for topics described above (these include lay articles, scientific articles, database resources, and informative websites):

Butterflies in the UK:

http://www.guardian.co.uk/environment/2009/apr/27/butterfly-decline-conservation-endangered-species

http://www.dailymail.co.uk/sciencetech/article-1193247/The-blues-Butterfly-species-reborn-30-years-extinction.html

 ** photo of blue butterfly at top of post, from The Guardian

Amphibians and signal species:

http://nationalzoo.si.edu/Animals/ReptilesAmphibians/Exhibit/Topics/amphibian_conservation.cfm

Great Sci Am blog on extinctions:

http://www.scientificamerican.com/blog/extinction-countdown/index.cfm?&offset=41

State of pollinators, like honeybee colony collapse disorder:

http://books.nap.edu/openbook.php?record_id=11761&page=1

http://www-chem.umd.edu/news/posts/452

 http://riley.nal.usda.gov/nal_display/index.php?info_center=8&tax_level=2&tax_subject=10&want_id=1322&topic_id=1006

http://www.scientificamerican.com/article.cfm?id=saving-the-honeybee

http://www.the-scientist.com/blog/display/55919/

Chronic Wasting Disease

http://www.ncbi.nlm.nih.gov/pubmed/11974617

 http://www.cdc.gov/ncidod/dvrd/cwd/

http://www.cwd-info.org/

http://www.cdc.gov/eid/content/15/5/pdfs/696.pdf

white nose syndrome

http://www.fws.gov/northeast/white_nose.html

http://www.nwhc.usgs.gov/disease_information/white-nose_syndrome/

http://www.scientificamerican.com/article.cfm?id=night-stalker-white-nose