There are countless definitions of weeds, ranging from the hardheaded
one necessarily observed by farmers, that a weed is any plant that
interferes with profit, to the aesthetic (a popular gardener's
definition of a weed is "a plant out of place"), to Ralph Waldo
Emerson's sanctimonious assertion that a weed is "a plant whose
virtues have not yet been discovered."

Lewis Ziska, a lanky, sandy-haired weed ecologist with the Agriculture
Research Service of the U.S. Department of Agriculture, speaks of
weeds with admiration as well as apprehension, and even with hope.
Ziska explores what global climate change could do to mankind's
relationship with weeds.

He took soil from an organic farm, which already contained seeds of 35
common weeds, and with it created uniform beds at each of the sites,
urban, suburban and rural, so that the growing medium and weed
population would be the same throughout. What happened over the next
five growing seasons surprised even him.

Not only did the weeds grow much larger in hotter, CO2-enriched plots
— a weed called lambs-quarters, or Chenopodium album, grew to an
impressive 6 to 8 feet on the farm but to a frightening 10 to 12 feet
in the city — but the urban, futuristic weeds also produced more
pollen. Five years after the creation of the plots, the biggest
ailanthus in the rural test site measured about five feet tall. The
city site boasted a 20-footer.

He traces his interest in weeds to an epiphany during his
undergraduate years at the University of California at Riverside:
noticing a weed springing up through a crack in the Southern
California pavement, he was suddenly struck with wonder at any
organism that could flourish in such a hot, dry, hostile environment.
That may become an essential talent, it occurred to Ziska, given the
way our planet is going.

When he grew ragweed plants in an atmosphere with 600 p.p.m. of CO2
(the level projected for the end of this century in that same
climate-change panel "B2 scenario"), they produced twice as much
pollen as plants grown in an atmosphere with 370 p.p.m. (the ambient
level in the year 1998). This is bad news for allergy sufferers,
especially since the pollen harvested from the CO2-enriched chamber
proved far richer in the protein that causes the allergic reaction.

In this new world that we have made, weeds, our old adversaries, could
be not only tools but mentors. At which point, if Ralph Waldo Emerson
is to be believed, weeds by definition will cease to exist.

-- 
Can Weeds Help Solve the Climate Crisis?
http://tinyurl.com/5sj4hj

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