We are in the early stages of a massive human-caused mass extinction. Some biologists at UC Santa Barbara ask an important question: since most of the threatened species can't be saved is there some way to identify which species are the worst to lose? Their answer: loss species with no evolutionary close relatives in their ecosystem will cause the biggest impact and most deserve saving.
(Santa Barbara, Calif.) –– The Earth is in the midst of the sixth mass extinction of both plants and animals, with nearly 50 percent of all species disappearing, scientists say.
Because of the current crisis, biologists at UC Santa Barbara are working day and night to determine which species must be saved. Their international study of grassland ecosystems, with flowering plants, is published this week in the Proceedings of the National Academy of Sciences.
"The current extinction event is due to human activity, paving the planet, creating pollution, many of the things that we are doing today," said co-author Bradley J. Cardinale, assistant professor of ecology, evolution and marine biology (EEMB) at UC Santa Barbara. "The Earth might well lose half of its species in our lifetime. We want to know which ones deserve the highest priority for conservation."
Think of this as development of rules for triage. Technology combined with the human instinct for reproduction is going to wipe out a large fraction of other species. For those few of us who believe that such species loss is a really bad thing what types of species conservation should we support? It is an important question.
Recent studies show that ecological systems with fewer species generally produce less biomass than those with more species. Less plant biomass means that less carbon dioxide is absorbed from the atmosphere and less oxygen is produced. So, as the biomass of plants plummets around the globe, the composition of gasses in the atmosphere that support life could be profoundly affected. Additionally, there are fewer plants for herbivorous animals to eat. Entire food chains can be disrupted, which can impact the production of crops and fisheries.
The loss of species that are not closely related to other species in the ecosystem reduces productivity more than the loss of species with close relatives. And the more genetically distinct a species is, the more impact it has on the amount of biomass in an ecosystem.
"Losing a very unique species may be worse than losing one with a close relative in the community," said Oakley. "The more evolutionary history that is represented in a plant community, the more productive it is."
Cadotte explained that the buttercup is a very unique species, evolutionarily. Losing the buttercup, where it occurs in grasslands, would have a much bigger impact on the system than losing a daisy or a sunflower, for example. The latter species are closely related. Each could therefore help fill the niche of the other, if one were to be lost. The daisy and sunflower also have a more similar genetic make-up.
"These 40 studies are showing the same thing for all plants around the world," said Cardinale. "It is not a willy-nilly conclusion. This study is very robust. It includes studies of plants that are found throughout the U.S., Europe, and Asia. We can have a high degree of confidence in the results. And the results show that genetic diversity predicts whether or not species matter."
Cheap DNA sequencing will tell us more about species relatedness. But even if we can find out which species are most important to save will we even be able to protect enough ecosystems to keep the important species around? I'm skeptical. 9 billion people are going to cause massive habitat destruction.
|Share |||Randall Parker, 2008 October 20 10:36 PM Trends Extinction|