How did english settlers at jamestown change the environment?

Summer in Jamestown, with tropical humidity and oppressively high temperatures, bred mosquitoes and biting flies. And winters, as the settlers soon discovered, were as cold as the summers were hot, But Jamestown colony almost failed because the Virginia Company made a poor choice when they decided where to establish it, and they were unable to successfully work together; the colony was a success because it survived, due to tobacco and the fact that the local Native American tribes were not able to destroy it because they were suffering from starvation and illness brought by the colonists.

Ais 190 b is 200c it can't be more then 100%