A study in the latest issue ofWeed Sciencesays that increased levels of carbon dioxide in the atmosphere benefit at least one species – weeds. Carbon dioxide acts as a fertilizer to invasive exotic grasses, resulting in higher growth rates and larger leaves. These stronger plants are also proving more resistant to the world’s most important herbicide, glyphosate, the study says.
It reports the effects of elevated carbon dioxide levels on four species of grass, all invasive exotic plants in Australia that previously have been controlled with glyphosate. The plants were grown in greenhouse experiments at ambient and elevated carbon dioxide levels.
Mature plants were then sprayed with the recommended amount of glyphosate. When treated with the herbicide, three of the four species showed a significantly higher survival rate under the elevated carbon dioxide level.
The study says pre-industrial carbon dioxide levels were rated at 280 parts per million (ppm), while 2005 levels reached 379 ppm. By the year 2100, it is predicted that carbon dioxide will reach 700 ppm. This level was represented in the elevated growth test.