Urban tree expert called in to preserve stately elms on National Mall

The elm trees that ring the National Mall in Washington, D.C., have stood witness to presidential inaugurations, given shaded respite to marchers and protestors, and provided millions of tourists with fresh air amid one of the busiest cities in the world.

But all that activity has taken its toll on the trees. A team of Cornell scientists is working to preserve the elms for generations to come.

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