Yes I am a botanist.
It is true that the climate is changing so rapidly that living things will have a hard time to adjust. The thing is, that the composition of our landscapes has been different in the past as well - the difference is the rate of change. That is, the climate is shifting and changing so fast, that it may happen too quickly for things to evolve into new niches and to develop new interactions with other organisms... not to mention the changing phenology of many living things. And, like you said how we have altered the landscape with impermeable boundaries such as roads, development, etc.
Carbon dioxide is responsible for most of the warming of the atmosphere, and we cannot remove what has already been deposited into it. We can, however, stop putting more in, and prevent truly disastrous changes from happening to future generations of humanity. This is the gist of the concept of living sustainably - not wasting, using what you need to live, not living to use. You know, the whole "reduce, reuse, recycle"... and then purchase recycled products to complete the cycle..