Weeds and global warming

For two decades, we’ve been battling noxious weeds in the natural restorations we manage. Two that have been attacked with greatest intensity are garlic mustard in the woods and field (Canada) thistle in the prairies. Since there are only two of us and an occasional hired hand, the task has been daunting.

We began with garlic mustard. Pulling seemed the most sensible control technique for scattered weeds. For several years, we spent at least two weeks each spring pulling it. We soon developed allergic reactions, and had to limit our work to two hours a day, extending the two weeks to nearly two months.

As more people became aware of the scourge, new control techniques were tested and found successful. We tried each as it became accepted.

Next, we burned. That worked nearly as well as pulling, and took far less time.

Finally, acknowledging the weed a worthy adversary, we used herbicides. At times, we seem to be winning the battle. At least our woods are in much better condition and the native flora are more abundant than in neighboring properties. But experience has taught us that any lapse in attention is rewarded by a new eruption.

Next was field thistle, which we were legally obligated to eradicate. Ten years ago, we had several small patches. An application of herbicide followed by slicing off each start at the root twice a week eliminated all of them within two growing seasons.

Last year, some appeared in a newly planted prairie. Having taken on another large new project, we overlooked them. This year, we were rewarded by huge patches to deal with, a challenge much larger than we expected.

After a few years of battling garlic mustard, we discovered research stating that excess nitrogen discharged to the ecosystem by fossil fuels encouraged the growth of plants with weedy characteristics. This fueled our interest in renewable energy sources, which is now our main professional focus.

Recently, CO2 has been implicated in the excess growth of weedy plants.

Now, global warming had been recognized as contributing to accelerated growth of weedy plants such as garlic mustard and field thistle and noxious weeds, including poison ivy and ragweed. It also is contributing to increased efforts and expenses for gardeners and farmers.

Unfortunately, commonly employed control techniques are no longer successful or far less successful than in the past. As weeds and ecosystems move farther north, simply using herbicides to eliminate them does not seem to work. According to Adam Markham, organizer of a symposium for the annual meeting of the American Society for Agricultural Sciences, attempts to “simply move crops northward or deal with . . . weed populations with herbicides are misguided. The processes at play are much too complex.”

Nitrogen, CO2, and climate change are leading to the loss of 2,300 acres of productive land each day at a cost to our economy of more than $13 billion annually. All are believed anthropogenic, resulting from using fossil fuel to feed our insatiable energy appetite.

What changes in energy production are needed to offset these staggering losses? How soon must we act?

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