Global Warming The Cause of Worsening Allergies?

(Thanks to JB for the link to this story.) The National Wildlife Federation says that allergy sufferers are suffering more today than 20 years ago because global warming is helping to create more pollen over a longer period of time.

If one were to try to rationalize this, wouldn't one say that the National Wildlife Federation should be thrilled with more pollen and therefore, more wildlife growth?