All I can say is look very carefully if choosing "tree planting" to offset emissions.<p>The first caveat is that the trees are <i>planted</i>, but may not necessarily live, and even if they do live for a while, it may take decades before they actually cause an "offset".<p>The second is that trees that are planted are sometimes harvested, causing the offset to be negative, given that fossil-fuels are almost certainly used in the harvesting and processing of the wood.<p>The third is that the trees are likely to be plantation trees -- ie, a monoculture with little to no wild-life value. Wild-life value is important, because trees aren't things, they're normally part of an ecosystem that sustains itself, adds to soil carbon, and so on.<p>Or you could find a way to buy and plant and care for your own trees, and use your own labour, which would be a thoroughly honest way to go. Having planted a lot of trees, there's nothing like looking at a tree you planted 10 years ago and is used by birds and insects and shade for animals.<p>Lastly, if you do have thousands of USD, possibly the best carbon offset is to either fund a activist group to get in people's faces about the larger problems, or to buy political influence to pass more environmental protection legislation.