'urban forests are suffering partly because “so many of the trees we grow don’t belong here and aren’t sustainable without plentiful supplies of imported water.

'urban forests are suffering partly because “so many of the trees we grow don’t belong here and aren’t sustainable without plentiful supplies of imported water.” “Historic photos of the region show coastal shrubs, oaks on the foothills and sycamores along streams and rivers,” he said. “Yet, we planted way too many trees from areas that get two to three times as much rain as we do.”' What may be worrying is if these drought-stressed trees are cultivating an artificially high population of pests that will then put added stress on the sustainable population of native drought-tolerant trees.