Developers don't like saving trees; it forces them to adjust the lot grading and road patterns for tree preservation rather than efficiency. The installation of services and construction disrupts the water table and the trees sometimes die anyways. Purchasers complain that crap from the trees is sticking to their cars. It is just easier for everyone to flatten them and stick in some cheap twig.
Now the State of Virginia is going to insist that developers preserve "some percentage" of their parcel's original trees. Environmentalists tell the Washington Post that "Losing a big tree means losing a valuable sponge for storm water, a root system that prevents erosion, and a filter that removes carbon dioxide and the precursors of smog.
"You get dirty water, and polluted everything," said Gary Moll of the conservation group American Forests. In a 2002 study, his group found that the Washington region's trees contained enough carbon to offset the annual emissions from more than 2,900 cars.
If saving old trees proves impossible, the developers would replant trees or pay to preserve them elsewhere. But local jurisdictions have the option of following it or not; most local jurisdictions are controlled by developers, which is why one needs state-wide rules.
Also, planted trees rarely get big; the soil is usually over-compacted and the species chosen do not grow as tall as the old elms and other trees that have grown up in older areas. It should not just be an either-or.
A deciduous tree planted on the south side of a house is the ultimate passive solar system; it shades in summer and lets the sun through in winter. Let's use this time out in the housebuilding industry to develop codes and bylaws that make appropriate tree planting part of the requirements for the construction of any home.