Greetings listeners, and welcome to the fifth Dispatch from the Endocene. I want to thank Extinction Radio for hosting another episode on their website, where they will be posting links for further reading on the topics in this segment.
Last week I said I expected to be talking about the ghastly moose situation, but since then a couple of other things seem more dire unless, of course, you are a moose. Still, I’ll save them for another time. One thing is certain - there is no lack of material when the subject is the spectacular ongoing crash of biodiversity on planet Earth. That is, for anyone who is the least interested, and unfortunately, most people aren’t. If you are still listening, you are in a very tiny exclusive cohort.
After a four-year review, the US Fish and Wildlife Service has confirmed this week that the Eastern Cougar, also knows as a puma, or panther, is officially extinct. This is felicitous, because it lightens up the load on the burgeoning endangered species list. It has been eighty years since the last known specimen was killed in New England, so what took them so long to declare it extinct? And what does that have to do with calculating the number of species that are going extinct today - and how massive is the 6th mass extinction, really?
I want to illuminate these inquiries with a study from 2007 titled: Are we in the midst of the sixth mass extinction? A view from the world of amphibians. Frogs, salamanders and caecilians (Sicilians) are considered to be the most at risk compared to any other taxon, which makes the scientists sad, because most of those amphibian species already managed to survive four mass extinctions and thus, are called “sentinels of environmental health.” In other words, if the amphibians can’t make it through humanity’s influence of pollution, habitat destruction and epidemic fungal disease from global warming having survived this far, it doesn’t bode well for all the other, more recently evolved, life forms. The paper informs us that, quote:
“The rate of extinction of amphibians is truly startling. A recent study estimates that current rates of extinction are 211 times the background extinction rate for amphibians, and rates would be as high as 25,000–45,000 times greater if all of the currently threatened species go extinct….”
“What Is the Principal Cause of the Present Extinction Spasm?” the scientists wonder, and then write
“Human activities are associated directly or indirectly with nearly every aspect of the current extinction spasm. The sheer magnitude of the human population has profound implications because of the demands placed on the environment. Population growth, which has increased so dramatically since industrialization, is connected to nearly every aspect of the current extinction event. Amphibians may be taken as a case study for terrestrial organisms. They have been severely impacted by habitat modification and destruction, which frequently has been accompanied by use of fertilizers and pesticides. In addition, many other pollutants that have negative effects on amphibians are byproducts of human activities. Humans have been direct or indirect agents for the introduction of exotic organisms.”
“Furthermore, with the expansion of human populations into new habitats, new infectious diseases have emerged that have real or potential consequences, not only for humans, but also for many other taxa, such as the case of Bd and amphibians. Perhaps the most profound impact is the human role in climate change, the effects of which may have been relatively small so far, but which will shortly be dramatic (e.g., in the sea). Research building on the Global Amphibian Assessment database showed that many factors are contributing to the global extinctions and declines of amphibians in addition to disease. Extrinsic forces, such as global warming and increased climatic variability, are increasing the susceptibility of high-risk species (those with small geographic ranges, low fecundity, and specialized habitats).
“Multiple factors acting synergistically are contributing to the loss of amphibians. But we can be sure that behind all of these activities is one weedy species, Homo sapiens, which has unwittingly achieved the ability to directly affect its own fate and that of most of the other species on this planet. It is an intelligent species that potentially has the capability of exercising necessary controls on the direction, speed, and intensity of factors related to the extinction crisis. Education and changes of political direction take time that we do not have, and political leadership to date has been ineffective largely because of so many competing, short-term demands. A primary message from the amphibians, other organisms, and environments, such as the oceans, is that little time remains to stave off mass extinctions, if it is possible at all.”
Notice the emphasis on the oceans, in a paper written almost ten years ago - and voila here we are with news of massive die-offs in the Pacific grabbing the headlines, such as an article from the Seattle Times declaring “Toxic algae bloom might be largest ever”. That story quoted a scientist who said, quote, “The fact that we’re seeing multiple toxins at the same time, we’re seeing high levels of domoic acid, and we’re seeing a coastwide bloom — those are indications that this is unprecedented.” unquote. So the fish and shellfish are being poisoned, and so are animals that eat fish like sea lions and birds. The coast has been closed for harvesting clams, geoduck, scallops, mussels, oysters and others. The article mentions nutrient availability, much of which is from sewage, agricultural fertilizer run-off, and nitrogen deposition from burning fuel.
However, another insidious influence wasn’t mentioned, even though it was made famous in research published back in 2001 by Jeremy Jackson and numerous co-authors.
The paper described how historical overfishing predated any of our more recent attacks on ocean life, after he realized that at the time Columbus arrived in America, there were millions upon millions of green turtles in the Caribbean. This study was a reminder of what a pristine ecosystem looks like, and its a far cry from what we have today. It places the primary reason marine ecosystems collapse on overfishing, back to pre-historical eras in some areas, which set the stage for algae blooms such as are now unprecedented on the west coast. I recommend reading the entire paper, especially to understand what happened in the Chesapeake Bay, which is an epic tragedy, but here’s an excerpt from the beginning:
“Few modern ecological studies take into account the former natural abundances of large marine vertebrates. There are dozens of places in the Caribbean named after large sea turtles whose adult populations now number in the tens of thousands rather than the tens of millions of a few centuries ago. Whales, manatees, dugongs, sea cows, monk seals, crocodiles, codfish, jewfish, swordfish, sharks, and rays are other large marine vertebrates that are now functionally or entirely extinct in most coastal ecosystems. Place names for oysters, pearls, and conches conjure up other ecological ghosts of marine invertebrates that were once so abundant as to pose hazards to navigation, but are witnessed now only by massive garbage heaps of empty shells.”
“Such ghosts represent a far more profound problem for ecological understanding and management than currently realized. Evidence from retrospective records strongly suggests that major structural and functional changes due to overfishing occurred worldwide in coastal marine ecosystems over many centuries. Severe overfishing drives species to ecological extinction because overfished populations no longer interact significantly with other species in the community. Overfishing and ecological extinction predate and precondition modern ecological investigations and the collapse of marine ecosystems in recent times, raising the possibility that many more marine ecosystems may be vulnerable to collapse in the near future.”
Let’s take one example from the paper that describes the knock-off effects of human hunting.
“Northern Pacific kelp forests presumably flourished before human settlement because predation by sea otters on sea urchins prevented the urchins from overgrazing kelp. Aboriginal Aleuts greatly diminished sea otters beginning around 2500 yr B.P., with a concomitant increase in the size of sea urchins. Fur traders subsequently hunted otters to the brink of extinction in the 1800s with the attendant collapse of kelp forests grazed away by sea urchins released from sea otter predation. Legal protection of sea otters in the 20th century partially reversed this scenario. However, kelp forests are again being depleted in areas of Alaska because of increased predation on sea otters by killer whales. The whales shifted their diet to sea otters from seals and sea lions, which are in drastic decline.”
After tracing numerous examples of ocean ecosystems around the world, the paper concludes:
“In summary, historical documentation of the long-term effects of fishing provides a heretofore-missing perspective for successful management and restoration of coastal marine ecosystems. Previous attempts have failed because they have focused only on the most recent symptoms of the problem rather than on their deep historical causes. Contrary to romantic notions of the oceans as the “last frontier” and of the supposedly superior ecological wisdom of non-Western and precolonial societies, our analysis demonstrates that overfishing fundamentally altered coastal marine ecosystems during each of the cultural periods we examined. Changes in ecosystem structure and function occurred as early as the late aboriginal and early colonial stages, although these pale in comparison with subsequent events. Human impacts are also accelerating in their magnitude, rates of change, and in the diversity of processes responsible for changes over time. Early changes increased the sensitivity of coastal marine ecosystems to subsequent disturbance and thus preconditioned the collapse we are witnessing.” end quote
Looked at this way, the sixth mass extinction began long ago, as weedy humans, like an invasive plant, migrated out of the habitat where they evolved in Africa, and rarely found resistance to slow our frenzied growth. Our collective blindness to the consequences of exponential will be our undoing. Hey, even the Pope, in his Encyclical, has said, “Doomsday predictions can no longer be met with irony or disdain.”
There’s not much to add other than to repeat Pogo’s trenchant observation as he surveyed a cartoon landscape for the first Earth Day in 1971, a vision the Pope now refers to as “an immense pile of filth”, which was that “We have met the enemy, and he is us”.
Thanks so much for listening to another Dispatch from the Endocene. I’ll be back next week with another, maybe.
cougar extinct: http://www.theguardian.com/environment/2015/jun/17/eastern-cougar-extinct-no-longer-needs-protection-says-us-conservation-agency
Seattle:
Are we in the midst of the sixth mass extinction? A view from the world of amphibians
Jackson paper: http://www.werc.usgs.gov/ProductDetails.aspx?ID=2570
videos from the Colloquia - In the Light of Evolution II: Biodiversity and Extinction
No comments:
Post a Comment