Reversing the Tide? Conservation Paleobiology, Rewilding & De-Extinction
That is where conservation paleobiology comes in. Largely pioneered by invertebrate paleontologist Jeremy Jackson, conservation paleobiology works by looking at the fossil record of the latest Quaternary and early Holocene to get a description of the biodiversity of the contemporary species prior to any significant influence of humans. Furthermore, more ancient crises (like PETM and mass extinction recoveries) give us evidence of how the biosphere reacts to tremendous rapid changes. This evidence from the fossil record allows conservation biologists to make better plans in dealing with current and near-future changes.
It has been noted that conservation paleobiology gives us a tremendous amount of useful data, such as:
Rewilding: If a species still persists in some region, but has undergone extirpation at another, it is possible to reintroduce it. But what about cases where the extinct taxon is globally extinct? It might be possible rewild it: that is, to introduce to a habitat a closely related species with similar biology and ecology to replace the original one. These efforts are already ongoing at various sites in the world, and generally show promise (so long as unwanted introduced invasives can be eliminated, too.)
Rewilding can benefit an ecosystem by restoring links that were once present, and thus increase the biodiversity and productivity of that region. This way habitats can be reestablished where key taxa are extinct. (In particular, megafauna tend to be major architects of ecosystems.) For instance, a great number of large fruits with huge seeds (like avocados) no longer have natural dispersers. That is because the animals which DID swallow these fruit and distributed the seeds are largely extinct: various proboscideans, giant ground sloths, big marsupials, giant tortoises, etc. (depending on where you are on the planet). These are also the sorts of animals that have preferentially died out in the Pleistocene and Holocene extinctions.
A promising example of rewilding to reestablish an old link in an ecosystem is on Mauritius (a small island in the Indian Ocean, east of Madagascar). Although famous for the dodo, Mauritius had a number of other recent extinctions: in particular, two species of giant tortoise of the genus Cylindraspis. Like other living giant tortoises, these were fruit eaters. They were the major animals to eat the large fruit of the native ebony tree Diospyros egrettarum. This species is down to a mere 10 individuals on Mauritius, and a few hundred on a offshore island. These seeds of the ebony tree do not germinate well on their own. But introducing the giant Aldabra tortoise (Aldabrachelys gigantea) to that offshore island has resulted in a spread of the slow-growing ebony plant. Similar experiments elsewhere show that reintroduction of the Aldabra giant tortoise (in combination with removal of invasive plants and animals) help old ecosystems reestablish their links.
Pleistocene rewilding takes this to a greater extreme. Many ecosystems once relied on giant mammal species. Although the megafauna of the Pleistocene are gone, there are sometimes close relatives from some part of the world that might be used to "fill in" ecologically in regions like North America or Pleistocene Park (which actually IS an ongoing project) in boreal northeastern Siberia. The idea is to release ecological equivalents (lions or tigers for Panthera atrox; Indian elephants for mammoths, etc.; and so forth), to allow an approximation of the Pleistocene ecosystem to return.
There are some problems with this approach, however:
Theoretically, there are several approaches, now that fossil genomes have been recovered:
Two projects are ongoing. The so-called Lazarus Project is working to de-extinct the gastric-brooding frog Rheobatrachus silus, which was wiped out in the wild in the mid-1980s. Another team has attempted to clone the extinct-in-2000 Iberian ibex Capra pyrenaica pyrenaica (the clone died minutes after birth). And (although technically not totally extinct), the northern white rhino (Ceratotherium simum cottoni) has only three living members, all in captivity. The two females are too old to bear young. But sperm and eggs have been collected from various individuals, and in May 2016 it was announced that attempts will be made to fertilize the eggs and implant the embryos into the very closely related southern white rhino (C. s. simum).
If restored, the de-extincted species could be restored to the wild as in re-wilding, removing the objection to it being the wrong species. But a whole new set of problems arise:
And, of course, the whole "world has changed--and will change a lot more VERY soon--since the Pleistocene" issue applies. Is it worth billions of dollars to bring back wooly mammoths to a world in which their cold habitat disappears?
Perhaps the most important issue, though, is that conservation money is rather limited. There are many critically endangered habitats and species in the world today; does it make more sense to try and protect these, or try and bring back an extinct form?
But one thing that you, as a student of the fossil record, should NOT argue is that various species were "meant to die". As we have seen, extinction is NOT some preordained fate, even though it does fall on the majority of species. And in particular, Holocene and Pleistocene extinctions are largely (either directly or indirectly) OUR fault.
If you want more information and debates (pro and con) about the de-extinction concept, the TED conference in which the term was introduced is available online. Also, the 2014 Howard Hughes Medical Institute BioInteractive series of talks was about the Sixth Extinction and how we should respond.
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