Species that are moved away from their natural predators back home can displace native species in their new habitats, and scientists say the problem already costs Europe 12 billion euros ($16 billion) a year.

The study, which is likely to hold true for other continents too, means that the seeds of future, perhaps bigger, problems have literally already been sown.

The study compared the effects of “alien species””such as American ragweed, Canada geese or Japanese deer in 28 European countries.

The study’s findings indicated that it can take decades to figure out which alien species will be disruptive, and looking at those that arrived in 1900 was a better indicator of current problems than looking at those from 2000.

“This lag in the cause-and-effect relationship would mean that … the seeds of future invasion problems have already been sown,” said the study, published in the U.S. Proceedings of the National Academy of Sciences.

Birds and insects were quickest to get established in new habitats, helped by their mobility. Others took far longer to reach the critical numbers to become invasive.

Introductions to Europe from the 19th century included ragweed, whose pollen is blamed for some hay fever, and the black locust tree, also from North America, which can damage European grassland with its ability to store nitrogen.

Increasing trade and travel during the 20th and 21st centuries means that the problems are likely to worsen unless checks on everything from the ballast tanks of ships to coffee or grain imports are tightened.

“We should do more about this problem now,” said Stefan Dullinger, of the University of Vienna, Austria, who was among authors of the study from institutes in New Zealand, the Czech Republic, Germany, Switzerland, Spain, Italy and France.

“Otherwise, things can become even much worse than they are in a few decades,” he said. The findings for Europe were likely to be mirrored elsewhere in the world.

The study also recommended that Europe should target controls at animal and plant species that were so far causing no damage but were known to be invasive in other habitats.

Climate change could also add to the spread. “Warmer temperatures could trigger the spread of invasive species that are limited by climate now,” Dullinger said.

Once upon a time, before the advent of synthetic weed killers for the lawn in the late 1940s, most American lawns contained white clover. Because no formulation of weed control could be developed that left both grass and clover, but killed everything else, clover was then lumped in with the weeds in subsequent marketing campaigns.

The scientist who developed 2,4-D, the most common synthetic herbicide, was publicly apologetic because his new product had the unfortunate side effect of eliminating clover. “The thought of white Dutch clover as a lawn weed will come as a distinct shock to old-time gardeners,” wrote Dr. R. Milton Carleton in his book, A New Way to Kill Weeds in 1957. “I can remember the day when lawn mixtures were judged for quality by the percentage of clover seed they contained. The higher this figure, the better the mixture.”

Today’s newfound emphasis on natural lawn care has folks taking a second look at clover as a primary lawn plant. The benefits are numerous:

Six Good Reasons White Clover Is Not a Weed

1. It’s low growing and needs little mowing.
2. It’s evergreen even in the coldest climates.
3. It’s drought tolerant, requiring little if any supplemental water once established.
4. It’s a fertilizer factory for grass and other plants since clover has the ability to store atmospheric nitrogen in its root systems.
5. It masks the presence of other weeds in the lawn.
6. It resists insects and diseases, especially the white grubs that can be a major lawn nemesis.

Paul Tukey is the founder of Safelawns.org. See all his Organic Lawn Care Tips.

There are 239 billion green opportunities in China. That is, China is planning on spending Y2 trillion ($239 million) to ensure that renewable energy will account for 15% of the nation’s power by the year 2020. China is the world’s second largest energy user. A country one fourth the size uses more.

Presently, less than 10% of China’s power comes from renewable energy. The government has earmarked Y1.4 trillion from 2006-2010. The U.S. says the clean technology market in China will be about $186 billion in 2010 and grow to $555 billion by 2020. Okay, I lost track of how much money can be made.

Looking for a good business opportunity? Help China become greener. They’ll pay out the gazoo for any good idea you can come up with. The best ideas – clean coal and carbon capture technologies says one expert.

Do you have a green idea?