Tree of Heaven --Noxious Weed or Savior of the Planet?
Ailanthus altissima is considered a weed by many.
It can grow five feet a year and is able to spring up in places with poor soil and little water.
A Harvard biologist, Peter Del Tredici, who teaches in the graduate school of landscape architecture,
says it, and invasive plants like it, may be the savior of the planet.
In areas of cities where nothing else will grow, it thrives in neighborhood pockets providing shade, fixing carbon, and producing oxygen.
Del Tredici has spent six years writing Wild Urban Plants of the Northeast, and he is at odds with native plant enthusiasts.
His view of plants that many of us call invasive is that they are responding to harsh conditions created by humankind.
They are not so much forcing native species out as flourishing in the most alien and hostile environments—cracks in sidewalks, poor and compacted soil—where natives will not grow.
Some are coastal plants who tolerate the road salt that has built up in cities.
Most are accidental migrants from other continents.
The Queen of Heaven is one of those plants carried here intentionally.
It was brought from China in the 1840s and valued for its rapid growth and shade.
By the 1870s, however, people were beginning to be skeptical about it, and no one liked it by the end of the century.
Del Tredici says that as overpowering as these plants are, to revile them is more of a philosophical than a botanical statement.
In cities they typically make up 10% of the vegetation, but this percentage can rise to 40% in depressed cities like Detroit.
Even though they do terrible harm, they are responding to the mess humans have made of their planet.
They are, he says, the “symptoms of degradation, not the causes of it.”
New possibilities for Duckweed
A tiny flowering plant might be well-suited to two very big jobs: cleaning industrial animal pollution and providing clean biofuel.
Researchers have discovered that duckweed has an appetite for animal waste
and quickly converts animal waste to a leafy starch that can then be converted into ethanol.
The current source for most U.S. ethanol is industrial-scale corn farming.
Environmentalists dislike corn-based ethanol because large amounts of pesticides are used in the farming process, and the corn generates a great amount of waste. When the costs are added up, corn-based ethanol may prove little cleaner than gasoline.
Duckweed produces more starch per acre than corn, say researchers.
In small-scale laboratory tests, they have used the same technologies as the fuel industry
currently uses to produce ethanol from corn to convert duckweed starch to ethanol.
Because duckweed consumes nitrogen, phosphorous, calcium, and iron, it may also help to clean not only the lagoons in which farm waste accumulates,
but any type of wastewater.