Though it is important to protect green spaces for many reasons, perhaps the biggest reason is that plants clean our air. They do this by taking up carbon dioxide, one of the major greenhouse gases, and releasing oxygen back into the environment.

However, did you know that plants can clean the ground as well, through a process called phytoremediation.

Scientists discovered that certain plants use their roots to pull potentially toxic contaminants from the soil. The plants then trap and store the toxins in their cells, or convert them into less harmful chemicals.

For example, poplar trees and mustard plants have been used to remove petroleum contaminants and lead from polluted soil. In Chernobyl, Ukraine, scientists planted sunflowers to remove radioactive uranium from the ground and water.

After plants accumulate the pollutants around them, they are harvested and disposed of safely. Scientists have discovered many species that can help draw out mercury, cadmium, nickel, lead, arsenic, and other toxins in order to clean the soil.

Phytoremediation has several advantages. First, plants can clean large areas more cheaply than other methods. Also, because the process uses natural organisms, it does not introduce new chemicals into a contaminated site.

However, phytoremediation also has its limitations. Cleanup is restricted to the area reached by a plant's roots and to the specific pollutants the plant can uptake. The process can be a long one, especially when the cleaning plants grow slowly, like trees. Finally, wildlife may be at risk if the toxins accumulated in the plants enter the food chain.

In the end, while some plants may help us clean up the messes we've already made, it's far better to avoid dumping toxins in the first place.