Top: Large mature trees hold carbon in their tissues. 2:Recently green space in Fairfield/Gonzales, now sacrificed to development. 3:carbon-holding tissue. 4 and 5: Big gnarled and abused old monarch in danger, Rockland area.
Some local politicians and mayors have said that despite the Harper government's non-signing of the Kyoto agreement, policies against global warming can be pursued at the municipal level. Let's hope they remember that that would entail first and foremost, massive tree replacement. Tree removal is a much bigger cause of global warming than is the transportation sector, and there is a danger that an uninformed public will be lulled into thinking that if politicians promote public transport, we're being virtuously "green" and can forget about Earth's tree cover.
This is irrational, but when something is repeated often enough people believe it without examining the facts. The boreal forest of Canada and Russia is the best carbon sink on the planet, but urban tree cover also plays a part, due to the fact that the sprawling paved "heat islands" called cities contribute most to climate change. If local mayors are serious about mitigating climate change at the local level, they will have to change the patterns of development and beef up greenspace preservation policies radically. The biggest trees do the best job of carbon absorption, naturally enough; the smaller trees that often replace them whenever someone deems one "sick" or "dangerous" (which is code for inconvenient, to someone) do not do as good a job. The row planted at Vic High, for example, to replace those destroyed this year during construction, will especially in their young years do a lot less for the atmosphere than their predecessors did.
Big trees need big spaces; houses packed closely together lead to much more global warming than cars do, and both are a result of uncontrolled population growth in already-crowded areas.