Cassie Ammerman, Publicity
Are frogs a canary in a coal mine? We don’t actually know. What we do know is that amphibians have been disappearing for decades and all we have are theories of why. In their new book, Extinction in Our Times: Global Amphibian Decline, James P. Collins and Martha L. Crump have gathered everything we know about disappearing frogs and used it as a lens to see clearly the larger stories: climate change, conservation of biodiversity, and a host of profoundly important ecological, evolutionary, and ethical issues.
The following post is an excerpt from Extinction in Our Times, explaining why we should care about the loss of biodiversity in general, and why we should worry about frogs specifically.
Why Should We Care about Loss of Biodiversity?
Conservation biologists, philosophers, environmental ethicists, and others offer several key reasons to conserve biodiversity. One argument is that organisms have direct economic value for humans. We use plants and animals for medicines, food, clothes, building materials, recreation, and other luxuries and necessities. But what if an organism that is of no use to us for food or hides is screened for useful medicinal compounds and found to have none? Do we sanction its extermination? Why must a plant or animal be of direct economic benefit to humans to have worth? Economic value alone is not the only reason to preserve biodiversity.
Another reason often given…to conserve biodiversity is that organisms, as components of ecosystems, provide services, and their interactions with other organisms contribute to the overall healthy functioning of ecosystems… On a practical level, biologists want to know just how much the loss of a few species will reduce the quality of services within a specific ecosystem. Two schools of thought prevail.
One idea, called the “rivet hypothesis,” is that every species contributes to ecosystem integrity. The analogy is that biological species are like rivets in an aircraft. Only a limited number of rivets can be removed from an aircraft before it falls apart. Similarly, as species are lost, at some point ecosystem function becomes damaged.
The alternative view, called the “redundant species hypothesis,” suggests that high species richness is not necessary to ecosystem function. The argument is that as long as the biomass of primary producers, consumers, decomposers, and other trophic levels is maintained, ecosystems can function perfectly well with fewer species… Some ecologists suggest that even if all the organisms now considered to be threatened with extinction did indeed go extinct, other plants and animals would take over their roles and ecosystems would continue to function with scarcely a hitch.
Going from theory and empirical data for specific ecosystems to generalizations about all ecosystems, however, is a huge leap. Scientists are a long way from agreeing on which species (if any particular ones) are crucial to maintain productive ecosystems…
Why Should We Care if Amphibians Decline?
People differ in their concern over amphibian declines… Peter Daszak, who at the time was at the Institute of Ecology, University of Georgia, and his colleagues proposed that global declines of amphibian populations are “perhaps one of the most pressing and enigmatic environmental problems of the late 20th century.” At the other extreme, an editor emeritus of a Tennessee newspaper wrote: “We read an article recently that indicated that frogs are becoming an endangered species. The information in the article indicated that scientists (interested in frogs) were unable to explain what has happened. Personally, we have not missed the frogs as we have little contact with them.”
If we could chat with that editor emeritus, how would we convince him that conservation of amphibian diversity is important? Why should we care if amphibians disappear?
…We should care if amphibians disappear because we use them for our own benefit. Every year we use huge quantities of frogs…in medical research and for teaching purposes. Isolation, identification, and characterization of novel chemical compounds that occur in the granular glands of anuran skin have led to the development of new drugs for human use. In 2001, The Food and Agriculture Organization of the United Nations estimated the average quantity of frog legs sold for human consumption to be 4716 metric tons annually from 1987 to 1997. We buy millions of amphibians each year for pets: poison dart frogs, pacman frogs, White’s tree frogs, and fire-bellied toads to name but a few.
Amphibians play a key role in energy flow and nutrient cycling, in both aquatic and terrestrial environments. They…serve as “conveyor belts” by transferring energy from invertebrates to predators higher up on the food chain. This transfer of energy is efficient because amphibians expend relatively little energy to maintain themselves. About 50 percent of the energy an amphibian gets from food is converted into new tissue. That, in turn, is transferred to the next level in the food chain when a predator eats the amphibian…
Amphibians provide the world a valuable service through their eating habits. Tadpoles eat tremendous quantities of algae. In doing so, they alter the dynamics of aquatic ecosystems and reduce the rate of natural eutrophication (over-enrichment of water with nutrients, resulting in excessive algal growth and oxygen depletion). Most adult amphibians eat insects and other arthropod prey. A population of 1000 cricket frogs (Acris crepitans, small tree frogs about 3 to 3.8 cm long) consumes an estimated 4.8 million small insects and other arthropods annually.
Thus, both because of what they eat and because they serve as food for fish, reptiles, birds, mammals, and other animals, amphibians play a central role in the food web…
A world without amphibians would be an aesthetically less interesting place. Frogs serve as good luck charms for people all over the world, because of their association with rain. Frogs symbolize fertility—some species produce more than 20,000 eggs at a time. They represent resurrection, because they seemingly appear out of nowhere after heavy rains. Frogs are “magic.” How else could they transform from aquatic, algae-eating swimmers into terrestrial, carnivorous jumpers? From tadpole form to frog form?
Amphibians, especially frogs and toads, provide inspiration for our artistic endeavors. Many cultures have folk tales about a kissed toad turning into a handsome prince. Who could forget Mr. Toad in Kenneth Grahame’s The Wind in the Willows, or Beatrix Potter’s Jeremy Fisher… Archeologists worldwide unearth ceramic vases and vessels with anuran designs, and frog and toad images are woven into tapestries and carved into wood and stone.
Finally, from an ethical standpoint, we are obliged to respect and protect amphibians, just as we should respect and protect all other organisms. It is easier for people to respect organisms considered to be “good” than the “bad” ones such as malaria-carrying mosquitoes. As just indicated, most cultures value amphibians.