Declining Amphibian Populations

When April’s National Geo­graphic came in the mail, I ripped into it eagerly.  I flipped through the pages, look­ing at the breath-taking pho­tog­ra­phy, and saw an arti­cle on the world­wide frog cri­sis.  Imme­di­ately, I started talk­ing to the Spousal Unit about the arti­cle, and how I hoped to learn more.  I was expect­ing him to already have the basic knowl­edge that I had.  After all, he works for a research uni­ver­sity, in a depart­ment that specif­i­cally deals with ani­mal research. He also sends me cool sci­ence arti­cles, plenty of them about ecol­ogy, on a reg­u­lar basis. Plus, there’s a huge wall of infor­ma­tion about this very topic at our local zoo. Still, if he didn’t know about it, I real­ized that what I con­sid­ered to be com­mon knowl­edge prob­a­bly is not. I’ve done a lot of read­ing on this issue, so I’ll do my best to give a layman’s summary.

Since the 1980s, the world­wide amphib­ian pop­u­la­tion has been dis­ap­pear­ing.  This isn’t an iso­lated issue in cer­tain regions of the world, or only pre­vi­ously known threat­ened or endan­gered species. This is a mass extinc­tion, where the bio­di­ver­sity of the world is being destroyed. Yes, local issues play a part, but around a third of all amphib­ian pop­u­la­tions are threat­ened. In par­tic­u­lar, the frog pop­u­la­tion is dimin­ish­ing at an aston­ish­ing rate. The prob­lem has many roots, and isn’t com­pletely under­stood by sci­en­tists.  A few known fac­tors are habi­tat destruc­tion, cli­mate change, pol­lu­tion, and disease.

Since amphib­ians are affected by changes in both land and water habi­tats, they are dou­bly at risk when their world is pol­luted.  Amphib­ians take in needed oxy­gen through their skin. Deforestation deprives many of these ani­mals of a home. Humans hold most of the blame for habi­tat destruc­tion and pol­lu­tion that is dev­as­tat­ing their lands, of course. Sev­eral dis­eases are ram­pag­ing the pop­u­la­tions as well. The intro­duc­tion of non-native species, such as trout, also con­tributes to the decline.

The chytrid­iomy­co­sis, or chytrid, fun­gus is par­tic­u­larly vir­u­lent. (Actu­ally, can I really use the word “vir­u­lent” to describe a fun­gus? Oh well, I just did. Onward.) One the­ory is that the dis­ease orig­i­nated from African clawed frogs. These frogs were ini­tially exported for preg­nancy tests and make up the major­ity of frogs used in research at many uni­ver­si­ties today. Human scram­bling of ecosys­tems strikes again. Chytrid has spread to every con­ti­nent amphib­ians are found. It does not kill car­rier infant pop­u­la­tions, but adults are dying everywhere.

Amphib­ians play a vital role in the food chain, con­trol­ling rid of insect pop­u­la­tions and pro­vid­ing food for other ani­mals. That web is a del­i­cate bal­ance, and tam­per­ing with it can have unfore­seen effects on humans down the road. Frogs, espe­cially, are used widely in med­i­cines. They are filled with sub­stances that are of use to humans. Amphib­ians are used in all sorts of research, teach­ing us about the world. They are con­sid­ered bioindi­ca­tors. That very fragility that makes them sus­cep­ti­ble to changes in the envi­ron­ment is also used as an indi­ca­tor of gen­eral health. If all the frogs are dead, well, we’ve pretty much fouled things right up, haven’t we?

Humans may be to blame for many of the causes, but we’re also work­ing on solv­ing the issue. For the com­mon per­son, the most respon­si­ble step is to reduce your “eco­log­i­cal foot­print.” We should all be mind­ful of the way we’re walk­ing through the world in gen­eral any­way. Research into other issues, and inte­grated solu­tions are esca­lat­ing. Now that chytrid has been iden­ti­fied as a major cul­prit, there are some promis­ing advances in treat­ing by cap­ture and rere­lease into the home envi­ron­ment. Since tad­poles can be car­ri­ers, this is very hope­ful. The Amphib­ian Ark project focuses on pro­tect­ing a cap­tive pop­u­la­tion of 500 species to be released when­ever the cri­sis seems to have sta­bi­lized. Sci­en­tists are work­ing on regen­er­at­ing homes for these frog­gies. The video I linked to yes­ter­day is an exam­ple of the types of work that will be nec­es­sary to make ecosys­tems for ready amphib­ians to reinhabit.