Original landscape of American East

This New Scientist story is from January, but it's interesting -- streams and rivers across the eastern US were much more extensively terraformed by damming than ever thought:

Their analysis revealed that by 1840, there were more than 65,000 dams between South Carolina and Maine.

This revises the idea that the modern farming and damming practices are entirely responsible for certain observations:

"After every rainstorm, our creeks and streams run like chocolate milk," says Walter. The belief has been that the mud is dragged off eroded farmland and rushed down streams that were straightened and inflated by industrialisation.

But, Walter and Merritts say the sediment does not come from modern farms, but from those that capped the hills 300 years ago. Today, that mud still lines the ponds and streams, and every new storm simply dislodges it and moves it further downstream.

(via Jerry Pournelle)