|Credit: James Cornwell|
|Photo: Maureen Gilmer|
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Tamarisk, helpful to settlers, but pest in the long run
|Southern Xinjiang Railway |
"Aid agencies face pressure to provide quick solutions to long-term problems, so they recommend plants that thrive on degraded lands - in other words, plants with the attributes of weeds," Mr Low said today.
"Mesquite, a prickly firewood tree heavily promoted by the Food and Agriculture Organization of the United Nations, is now causing great suffering in Africa, where it is invading farmland and national parks."
"Sudan has passed a law to eradicate it, and Kenya and Ethiopia have declared it a noxious weed," Invasive species Biologist Tim Low said.
Lately I've noticed, in the face of Climate Change and Global Warming alarm, that there are a number of movements out there trying to downplay the dangers of change and invasive species as not being all that bad and we should accept the inevitable. We should learn to live with these consequences and adapt to the change. That is bunk. I'll never except human stupidity and make excuses and concessions for it. There has even been an attempt to downplay the bad role that invasives will play in destroying native species from their traditional habitats. Yet a new study came from the University of Toronto, shedding light on the reality of the serious situation and exposing the falsehood of that propaganda.
TORONTO, ONTARIO - Ecologists at the University of Toronto and the Swiss Federal Institute of Technology Zurich (ETH Zurich) have found that, given time, invading exotic plants will likely eliminate native plants growing in the wild despite recent reports to the contrary.
A study published in Proceedings of the National Academy of Sciences (PNAS) reports that recent statements that invasive plants are not problematic are often based on incomplete information, with insufficient time having passed to observe the full effect of invasions on native biodiversity.
"The impacts of exotic plant invasions often take much longer to become evident than previously thought," says Benjamin Gilbert of U of t's Department of Ecology & Evolutionary Biology (EEB) and lead author of the study. "This delay can create an 'extinction debt' in native plant species, meaning that these species are going extinct but the actual extinction event occurs hundreds of years after the initial invasion."
Much of the debate surrounding the threat posed to biodiversity by the invasions of non-native species is fueled by recent findings that competition from introduced plants has driven remarkably few plants to extinction. Instead, native plant species in invaded ecosystems are often relegated to patchy, marginal habitats unsuitable to their non-native competitors.
However, Gilbert and co-author Jonathan Levine of ETH Zurich say that it is uncertain whether colonization and extinction dynamics of the plants in marginal habitats will allow long-term native persistence. - "Of particular concern is the possibility that short term persistence of native flora in invaded habitats masks eventual extinction," says Levine.
The researchers conducted their research in a California reserve where much of the remaining native plant diversity exists in marginal areas surrounded by invasive grasses. They performed experiments in the reserve and coupled their results with quantitative models to determine the long term impacts of invasive grasses on native plants.
"Invasion has created isolated 'islands of native plants' in a sea of exotics," says Gilbert. "This has decreased the size of native habitats, which reduces seed production and increases local extinction. It also makes it much harder for native plants to recolonize following a local extinction."
"Our research also allows us to identify how new habitats for native flora could be created that would prevent extinction from happening. These habitats would still be too marginal for invaders, but placed in such a way as to create 'bridges' to other habitat patches," says Gilbert.
The findings are reported in the paper "Plant Invasions and Extinction Debts" in PNAS Early Edition this week. The research is supported by funding from the Natural Sciences and Engineering Research Council of Canada and the Packard Foundation. -
|Credit: James Cornwell|
|Credit: Benjamin Gilbert|
Many long time native Californians will remember this plant from the old days when they were once plentiful. The flower is called "Tidy Tips" (Layia platyglossa) and they were heavily growing on Rattlesnake Mountain in El Cajon when I was growing up as a kid in the 1960s. Unfortunately there is not a single plant existing up there any longer. I know because when I visited California in 2011, I made a deliberate attempt to look for it. What I remember most about the thick patches of them which grew interspersed with California Buckwheat & Coastal Sagebrush which also contained some Sea Lavender, was the biodiversity of insects, especially the butterflies population varieties which were very heavy. They too are now gone.