Biodiversity Losses Increase Risks of Domino Effect of Further Extinctions

This phenomenon is referred to as an “extinction cascade.”

New research shows that the loss of biodiversity can increase the risk of “extinction cascades,” where an initial species loss leads to a domino effect of further extinctions.

The researchers, from the University of Exeter, showed there is a higher risk of extinction cascades when other species are not present to fill the “gap” created by the loss of a species.

Even if the loss of one species does not directly cause knock-on extinctions, the study shows that this leads to simpler ecological communities that are at greater risk of “run-away extinction cascades” with the potential loss of many species.

With extinction rates at their highest levels ever and numerous species under threat due to human activity, the findings are a further warning about the consequences of eroding biodiversity.

“Interactions between species are important for ecosystem (a community of interacting species) stability,” said Dr Dirk Sanders, of the Centre for Ecology and Conservation at the University of Exeter’s Penryn Campus in Cornwall. “And because species are interconnected through multiple interactions, an impact on one species can affect others as well.

“It has been predicted that more complex food webs will be less vulnerable to extinction cascades because there is a greater chance that other species can step in and buffer against the effects of species loss.

“In our experiment, we used communities of plants and insects to test this prediction.”

The researchers removed one species of wasp and found that it led to secondary extinctions of other, indirectly linked, species at the same level of the food web.

This effect was much stronger in simple communities than for the same species within a more complex food web.

Dr Sanders added: “Our results demonstrate that biodiversity loss can increase the vulnerability of ecosystems to secondary extinctions which, when they occur, can then lead to further simplification causing run-away extinction cascades.”

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The loss of a predator can initiate a cascade, such as in the case of wolves, where their extinction on one mountain can cause a large rise in the number of deer. This larger number of deer then eats more plant material than they would have before. This reduction in vegetation can cause extinctions in any species that also relies on the plants, but are potentially less competitive, such as rabbits or insects.

Add this research to one of the many reasons why rigorously addressing climate change — which can destabilize environments — is of paramount importance.

Glow in the Dark Shark Species Discovered

The velvet belly lanternsharks look pretty unique.

Earlier this year a new species of deep water shark, Etmopterus lailae, was discovered in waters surrounding the Northwestern Hawaiian Islands in the Pacific Ocean.

Measurements of external features, teeth, vertebrae and intestines, along with specific external markings and patterns confirmed that it was indeed a new species – a member of the lanternshark family. Lanternsharks (Etmopteridae) are one of the most species-rich shark genera, with approximately 38 known species, 11 of which have been described since 2002.

The lanternsharks are one of two deep sea shark families to possess the ability to bioluminesce – in other words, they are able to glow in the dark. The other shark family with the ability to do this are the kitefin sharks (Dalatiidae). This family houses the infamous cookie cutter shark, which was known for its impressive ability to disable US Navy submarines in the 70s and 80s, by testing how the electrical cables and rubber sonar domes rated on a culinary scale (Johnson 1978). Imagine being the officer who had to report back about how the submarines were defeated by a particularly voracious … 22 inch (56cm) shark!

velvet-belly-lanternsharks

[…]

Bioluminescence is the emission of light as a result of a biochemical reaction. In contrast to fluorescence and phosphorescence, bioluminescenct reactions do not require the initial absorption of sunlight or other electromagnetic radiation by a molecule or pigment to emit light.

[…]

velvet-belly-lanternshark

Most fish bioluminesce by using their light organs (photophores) in one of two ways: harnessing the light produced by symbiotic bacteria or producing their own light through chemical reactions. However, shark luminescence works in a different way.

The organisation of the photophores strongly suggests that they are involved in varied behaviours, including anti-predatory response (camouflage) and intraspecies communication.