Trees cause global warming (isoprene) - Environmentalists and Biologists help!

Environmentalists and Biologists - please help me understand how much trees/vegetation contribute to Global warming? Please rate it compared to humans burning fossil fuels. Also - how is this changing as global warming progresses ?

This is with respect to Isoprene emissions from plants/trees.

Cite 1: “A trio of researchers from the Lancaster Environment Centre, in the UK has found that planting trees for use as a biofuel source, near populated areas, is likely to increase human deaths due to inhalation of ozone.”

Cite 2 : “Isoprene (C5H8 or 2-methyl-1,3-butadiene) is a highly reactive non-methane hydrocarbon (NMHC) that is emitted in copious quantities by vegetation and is responsible for the production of vast amounts of tropospheric ozone.

Cite 3 : “The evolution of natural isoprene emissions and physical climate over the next century will lead to continued tropospheric chemical change independent of changes to anthropogenic emissions.”

Terpenes help stimulate cloud formation. Therefore help cool the earth.

http://www.chemistryviews.org/details/ezine/5717791/Conifer_Scent_Influences_Climate.html

Just looking at the titles, the first two are referring to trees contributing to ground-level ozone, which is nothng to do with global warming (and nothing to do with the CFC-caused ozone hole in the upper atmosphere). Again, the trees are not contributing to climate change in any way; the only connection with climate change is that people talk about planting more trees to COMBAT climate change.

Secondly, this is pretty old news, and not actually relevant. Ground-level ozone – smog basically – is indeed bad for human lungs and for plants. To make smog, you need sunlight, hydrocarbons and nitrogen oxides. Hydrocarbons come from evaporating solvents and partly-burned gasoline and the like. But we’ve known for a couple decades that trees and other natural sources also actually give off a lot of hydrocarbons. So air pollution controls (for smog) are now focused mostly on the nitrogen oxides, since there really aren’t any natural sources of them, and if we keep nitrogen oxides under control, the hydrocarbons don’t matter.

Bottom line: sure, trees emit stuff that can in some conditions help form smog. But if we humans get our crap (cars, power plants) under control, those conditions will never happen. The second paper’s use of '‘responsible’ is pure crap.

That quote is on co2science.org, which also has “position papers” saying CO2 has nothing to do with climate change, and that it would not be relevant to discuss where they get their funding.

Thanks for the answers - I understand it better now. I was recently designing an Isoprene production plant (looks like there is quite an increasing demand for latex free materials like condoms and gloves) and looked up Isoprene.

Thanks again for the good answers.