Acid rain in North America was first discovered more than 40 years ago by ecologist Gene Likens. Acid rain is an environmental problem that has yet to be solved, according to Likens. He discovered acid rain while studying the Hubbard Brook Experimental Forest in New Hampshire’s White Mountains. 43 years-worth of data on acid rain and forest ecosystems, collected by him, Likens blames the combustion of relatively cheap fossil fuels for global warming and acid rain. Even though acid rain has been reduced through emissions standards set by the Clean Air Act and its amendments, the sulphur emissions that the law restricts have not been reduced enough, and nitrogen emissions, which it addresses very little, are increasing. The problem is at its worst in the Northeast. The region gets wind-blown emissions from coal and oil-fueled power generating plants in the middle of the country.