II am a biologist (kind of) and sudden changes in the environment usually causes massive extinctions. People think that the environment causes changes in species but that's the Lamarck theory which is obsolete. The Neo-Darwin theory says that species have mutations randomly and those mutations might help or not a individual to adapt to their environment. The most adapted survive and pass their genes to the next generation who could have another mutation with a similar effect to the old one and be even more adapted (take giraffe neck for an example).
In conclusion the environment does not make species evolve, the species mutates and the environment decides if that change fit or not in natural selection.