Climate Change Moves Weeds Around

As all of you probably already know, most of our neighborhoods have been inhabited and sometimes taken over completely by invasive foreign plants and weeds. In some cases these were plants that local authorities would be nice to add to the landscape and now they have taken over the landscape and no one can eradicate them. In other cases, immigrants brought plants and seeds from their homeland and planted them in their gardens, only to have them become invasive and disastrous to native landscapes. Here in Florida some prime examples include Kudzo, Brazilian Pepper Trees and Vines, Chokeweed, Spanish Bayonet, Spanish Needles, Hedge Bindweed and Air Yams. These foreign cultivars are aggressive and destructive and, in some areas, they carpet the landscape and crowd all other plants out.

But what does all of this have to do with global warming and climate change? Well, according to a new study it is now believed that climate change will likely shuffle some of the most troublesome weeds from their native local to far away farms and ranches, reeking havoc with cultivated crops. This study shows that a warming climate will provide prime conditions for invasive plants to get a foothold, spread quickly and crowd out native species. This study was performed by Princeton University Researchers and was recently published in the latest edition of the scientific journal Global Change Biology.

In some cases the outcome could be good, such as forcing invasives out of the west and allow the re-establishment of native species, but this opportunity will be short lived and the window for action will be limited. According to Bethany Bradley, a biogeographer at Princeton University and lead author on the study, “We’re going to have to be in the right place at the right time before something else gains a foothold.” This basically means that if we want to turn a bad situation into a good thing, we have to be poised for action and swift to move.

History shows us that nonnative weeds and plants followed in the footsteps of European settlers as they spread across the West. Even one of the West’s most famous symbols – the tumbling tumbleweed, (also known as Russian Thistle), isn’t American. It came, in fact, from Russia. And today, non native species of plants across the West cost millions of dollars in damage to farms and ranches, alter the flow of water and function of ecosystems, provide fuels for fast-burning wildfires, and force government agencies to spend millions in response.

I am sure you are all aware of invasive non native species in your own areas. The only recourse county extension and weed departments have is to give these new invaders a high priority and eradicate them swiftly, before they take over. Because of this possibility, Bradley and two other Princeton scientists wanted to look at how changing climate conditions would effect the spread of weeds.

The researchers used 10 atmospheric models predicting how the West’s climate will change by 2100. Then they compared predicted changes in precipitation and temperature with the most hospitable conditions for five of the West’s most obnoxious noxious plants: Cheatgrass, Spotted Knapweed, Yellow Starthistle, Tamarisk and leafy Spurge.

Cheatgrass, for instance, will likely move out of southern Nevada and Utah and move into Idaho, Montana and Wyoming. Although Cheatgrass currently dominates most of the mountainous regions in the west, it will have difficulty remaining there as the temperatures get warmer and the conditions get drier. .

Yellows Starthistle may expand in California and Nevada as the climate changes while Spotted Knapweed could spread to Montana, Wyoming, Utah and Colorado, the study showed.

Leafy Spurge will probably disappear from Colorado, Nebraska, Iowa and Oregon. Tamarisk is likely to be unchanged.

The models in the study take into account many of the possible scenarios of a warming climate, but it’s still difficult to predict changes at a local level. That’s especially true for precipitation, including when it will fall and how much. Many areas are suffering from long droughts while others are subject to year round flooding. None of this is currently predictable.

Ms. Bradley admits that this is a big gamble. She says that “even small changes in precipitation can have big impacts on invasive and native plants in the western U.S.” And just because climate may drive out one invasive weed, it doesn’t mean another won’t quickly set up shop, she said. That’s why it’s important to find viable native plants – even those that are only native regionally, not locally – that can get established before the arrival of another invader, she added.

This is why I believe that the best way to harmonize our natural environments on a local level is to re introduce native species and plant them in heavily. Local species, even those weeds that you don’t really like, are better for the native environment and once they get a toehold, they can keep the non native species out.

Another researcher in this landmark study, David Wilcove, said, in a recent statement that “the question for policy makers and land managers is, ‘What do we want these lands to be?’ ” He adds, almost like a warning of sorts, that “these lands will change, and we must decide now – before the window of opportunity closes – whether we do nothing or whether we intervene.”

Overall, the predictions made in the study should help weed managers know which plants to be on the lookout for and prepare for their arrival. Reacting to weed infestations gets expensive. Montana, for instance, spends $21 million a year on fighting weeds and needs to be spending $58 million just to deal of 5 percent of the weeds it already has, according to the Montana Weeds Control Dept.

In all cases the advice is the same. Prevention is the cheapest way to go.. and the easiest. If you let the weeds take over, it’s almost impossible to get rid of them. Just come down here to Florida and look at the fence next to my yard. Kudzo, from Japan, and Brazilian Pepper Vines, from Brazil, cover the landscape. If we had stopped this years ago, it might be Morning Glory, Sea Rockets and Marsh Mallows instead… and what a lovely beachside landscape that would make!

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