Deforestation is one major concern with harvesting wood. There are also all types of organisms that lose their habitats.
Past climate changes led to extinction of many species, population migrations, and pronounced changes in the land surface and ocean circulation. The speed of the current climate change is faster than most of the past events, making it more difficult for human societies and the natural world to adapt.
Species A and B would be the most similar because there is only one mutation between the two of them located in the first codon.
