According to the Brooklyn Eagle, there have been complaints about damage to trees due to the NYC Waterfalls. Here’s an excerpt from their article:

"The Public Art Fund’s dramatic NYC Waterfalls, a big tourist draw
throughout the summer, are scheduled to be turned off in October.

"But that may be too late for many of the plants and trees both near the
River Café and further down along the Brooklyn Heights Promenade.

"Two of the four dramatic waterfalls, designed by Danish artist Olafur
Eliasson, are near the Brooklyn waterfront, one under the Brooklyn
Bridge and the other between Piers 4 and 5. When they were turned on in
June, there was nothing but praise for them.

"‘An Environmental Assessment Study was done, and it was concluded that
there would be no lasting impact from the project,” said Rochelle
Steiner, director of the Public Art Fund.

"However, starting about a month later, there were complaints that the
partially salt river water that is being sprayed up through the
waterfalls was causing many of the trees and plants in the River Café’s
famed garden to become prematurely brown and yellow. Owner Michael
“Buzzy” O’Keefe planted the trees 32 years ago when he opened the
restaurant in the Fulton Ferry area."

The Brooklyn Paper also has a story today.

The Waterfalls have claimed another victim.

Trees, shrubs, and greenery along the fabled Brooklyn Heights
Promenade are showing severe signs of stress, and in some cases, death
— thanks to a constant battering of brackish East River water spewing
from Olafur Eliasson’s “New York City Waterfalls” project.

The Promenade foliage is just the latest victim of Eliasson’s four-headed killing machine. As The Brooklyn Paper reported earlier this month,
the waterfalls’ saline spray has severely damaged trees at the River
Café in DUMBO, turning their greenery a decidely autumnal hue.