Amphibians survived 4 previous mass extinctions over the last 350 million years,
but are now the most threatened major category of creatures, with 1/3 of species
already threatened. Amphibians have survived a much longer time and through
more drastic environmental changes than mammals have. If they're in trouble
that's an alarm bell indicating that conditions have reached a danger point,
and what does that say about what could be in store for us?
[ Are we in the midst of the sixth mass extinction? A view from the world of
amphibians, David Wake, Vance Vredenburg,
Proceedings of the National Academy of Sciences v105 suppl 1, Aug 2008,
www.pnas.org/content/early/2008/08/08/0801921105.full.pdf ]
Unlike other types of damage, species loss is likely to take millions of years
to recover, affecting 10,000 times more people than have lived in all of time
till now.
[ The biotic crisis and the future of evolution, Norman Myers, Andrew Knoll,
Proceedings of the National Academy of Sciences v98#10 p5389-5392 May 2001,
www.pnas.org/cgi/content/full/98/10/5389 ]
Are we really an intelligent species, or will we ignore the warnings that our life support system is unravelling? Dinosaurs were the dominant species for longer than mammals have been in existence so far. It remains to be seen whether dinosaurs will have the last laugh as far as proving to have what it takes to survive a long time.
It's popular to blame microbes for diseases, but we'll probably never know how much the diseases are due to weakened immunity caused by toxic disruption, and/or disruption of beneficial bacteria, fungi, and other micropredators and competitors that keep the pathogenic ones in check. (This also applies to people; for example diabetes has been linked to toxics, not to fats. Many are fooled into thinking fats are bad because many toxics concentrate in fats. If anyone knows of a single other study that separates out whether it's the fats or the toxics I'd like to know.)
Pesticides may be one of the significant reasons frogs are disappearing even in pristine places like Yosemite [Newsweek 13 May 2002 p46]. Atrazine, one of the most commonly used herbicides, is harmful to frogs at 100 parts per trillion, 120 times lower than EPA exposure limit. This was not discovered until 38 years after it was allowed on the market. It can be carried long distances on wind and rain. See references below.
Since frogs are insect eaters, insecticides are liable to be especially problematic. The more insecticides are used, the more frogs and other insect predators are messed up, so ultimately you're liable to get more insects. That's how pesticide companies make their living - if they can suck you into the vicious circle they laugh all the way to the bank.
While fungicides and herbicides are different, a similar phenomenon can occur,
by interfering with beneficial parts of the soil ecology that plants depend on,
thus shifting conditions in favor of weedier species. A farmer converting to
organic discovered some weeds disappeared when they stopped using Roundup [!].
[ kandmhfarm on sanet-mg sustainable agriculture email list 4 Jun 2000
www.ibiblio.org/london/orgfarm/crops/large-scale.weed-control
or lists.sare.org/archives/sanet-mg.html ]
Of course there are plenty of other types of toxics floating around, as well as things that are not necessarily toxic but can be significantly disruptive if there's too much, such as fertilizers, hormones, pharmaceuticals.
But then it's also unlikely there's any one single factor, it's more likely there are just too many negative factors for them to deal with all at once.
While people are the cause of a lot of the problems and it's understandable to be drawn to pristine areas, I believe people can also be the cause of solving the problems, and overlooked opportunities for conservation are to tap the large pool of people-power available in urban areas, which has the potential if done right to turn things around faster and more economically there than in rural areas, even if starting from more degraded conditions. Urban areas can also be laboratories for trying different strategies to find out what does and doesn't work, which can then be used to achieve greater effectiveness in larger remoter areas.
For more general info:
Amphibian declines: an issue overview, JK Reaser 2000, Federal Taskforce on Amphibian Declines and Deformities, www.frogweb.gov/declines.pdf
en.wikipedia.org/wiki/Decline_in_amphibian_populations
amphibiaweb.org/declines/declines.html
For what we can do:
Amphibian Conservation Alliance www.frogs.org has action alerts; they started in Berkeley and Oakland so there may still be local connections despite moving its office to the Washington DC area
Partners in Amphibian and Reptile Conservation has habitat management guides at www.parcplace.org/habitat_management_guide.html
references:
The lethal impact of Roundup(R) on aquatic and terrestrial amphibians. Relyea, R.A., Ecological Applications 15:1118-1124 2005
The lethal impacts of Roundup and predatory stress on six species of North American tadpoles, Relyea, R. A., Archives of Environmental Contamination and Toxicology 48:351-357 2005
The impact of insecticides and herbicides on the biodiversity and productivity of aquatic communities, Relyea, R. A., Ecological Applications 15:618-627 2005
For details see www.pitt.edu/~relyea/Publications.html and its link to abstracts and reprints.
Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low ecologically relevant doses, Tyrone Hayes etal, Proceedings of the National Academy of Sciences v99 i8 p5476(5) 16 April 2002 www.pnas.org/content/99/8/5476.full.pdf
Atrazine-Induced Hermaphroditism at 0.1 PPB in American Frogs (Rana pipiens): Laboratory and Field Evidence, Tyrone Hayes etal, Environmental Health Perspectives v111#4, April 2003, www.ehponline.org/members/2003/5932/5932.html
Pesticides and Flawed Frogs, Carl Hall, SF Chronicle 9 Jul 2002 www.mindfully.org/Pesticide/2002/Flawed-Frogs-Pesticide-Deformed9jul02.htm
-- Walter Epp for7gen àt idiom døt com