poplar trees are being used to clean chemical pollutants from the groundwater.
if i remember correctly, the normal way to remove trychloralethylene (TCE) from the soil is to dig all of the soil up (generally many tons of it), run it through a furnace hot enough to burn off the TCE and then put the soil back in place. it is a very expensive and energy-intense process that destroys the topsoil delaying the biological recovery of the site.
for reference, the sky is still falling. financial problems still pose major risks to our immediate future worldwide, but that is kind of old news at this point. the news related to our biological future is more interesting today.
so long as we're talking about money. if i had money today, i'd buy land somewhere and put hardwood trees on it. something that'll take 50 yrs to mature. in 50yrs, all of the naturally occurring high quality hardwood trees will be gone or protected, but the demand for the wood will be higher as people seek more natural-feeling high quality products. quality can't be faked. crazy hybrid GE hardwood trees could be invented that grow quickly, but hardwoods are desirable specifically because they grow slowly. that is what gives the wood it's fine grain and dense structure.