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Snippets

Maritime: Coral reefs also export biodiversity to other ecosystems. Getty ImagesWhen reefs give birth to sea creatures

Coral reefs give birth to a dazzling number of new species of sea creatures, according to a study that highlights their critical role in marine ecosystems. Scientists have found that the reefs not only harbour biodiversity, but are actively involved in the generation of new life forms. The study overturns conventional thinking that much of the sea life in coral reefs originated elsewhere.
Wolfgang Kiessling of the Humboldt University of Berlin, who led the study, said, “We found that coral reefs are very active at generating biodiversity in the oceans, and that they export biodiversity to other ecosystems. This was a surprise because many people had assumed that reefs were ecological attracters – that species go there from other places.”

He and colleagues in Germany and the US studied a database of fossil organisms that lived on the sea floor from the Cambrian period, about 500m years ago. They compared the number of new genera that first appeared in coral reefs with those in other shallow-water environments and found the reefs were responsible for about 50% more.

The team looked at fossils of so-called benthic organisms, such as starfish, clams and corals that live on the seabed. They ignored fossils of fish, which do not offer clues to where they evolve, because after they die their remains can float elsewhere.

Kiessling said,  “If we lose the coral reefs we lose the ability for marine ecosystems to generate new species in the future. I suspect that new species evolve every single day, but unfortunately not as fast as they go extinct.” Increasing carbon dioxide in the atmosphere damages coral as seas become warmer, which causes the coral to bleach, and become more acidic, which makes it hard for the tiny animals to repair their exoskeletons.

Experts say the world has already passed the safe level of carbon dioxide in the atmosphere for coral reefs, and even the most ambitious carbon cuts planned for coming decades will fail to save them.

David Adam
The Guardian


A question of plant biodiversity
The year of biodiversity has environmentalists mulling over a study that says plant biodiversity is in for a toss. As the warming proceeds, the levels of nitrogen and carbon dioxide—the two most important driving factors of plant growth—would increase. Darwin’s survival of the fittest would come into play as the most abundant plant species would dominate thus reducing species richness and, in turn, threatening plant biodiversity.
From 1997 to 2007 scientist Peter Reich conducted an experiment in which various species of perennial grasses were grown under all combinations of ambient and elevated levels of carbon dioxide and  of nitrogen dioxide. Over 10 years, the results showed that elevated levels of nitrogen are more harmful to survival of the less dominant plants than elevated levels of CO2 .
Under ambient levels of CO2, the increased levels of nitrogen reduced plant biodiversity by 16 per cent. But when levels of both were elevated, only eight per cent of the plant species were threatened, which shows that increased levels of CO2, at ambient levels of nitrogen had negligible impact on the plant species’ survival. The study specifically showed that under a nitrogen-enriched atmosphere, C3 grasses like rice, wheat, barley would be dominant. As these crops also need more water to grow, under conditions of drought they could leave the C4 grasses such as maize, sugarcane and millets with hardly any minerals or water for uptake.
“The dominant limiting resource (N) is the main driver of reduced species richness,” said Reich, scientist with the department of forest resources at the University of Minnesota in USA. Nitrogen is an element plants need to fight each other for. So if its levels increase, the species that can absorb nitrogen more efficiently, would produce more food; its growth would increase, thus pushing the weaker species out of the picture. Said Reich, “Rising CO2 might also indirectly impact biodiversity. That has not been addressed by my study. We need to pay attention to the direct and indirect ways in which CO2 influences plants, their diversity and productivity.”

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