Land use issues and transportation issues are two sides of the same coin: they are so inextricably bound together that you cannot discuss one without discussing the other. As the population has increasingly spread out over previously undeveloped land away from urban centers, the land use patterns of the Bay watershed have spurred development of an increasingly decentralized road network and have been a factor in the increasing the annual average mileage that residents drive. This expansion of the number of vehicles and miles driven also has created a situation in which more ecosystem impacts are felt.

Our transportation system relies on the automobile as the principal means of transportation.  Commercial and other interests design their stores and services to be able to be easily accessed by autos.  This translates to an increase in roadways, rooftops and parking lots adding to the level of impervious surface.  When the loss of wetlands and forested and vegetative land cover (the natural systems that filter out pollutants) are combined with the spread of roads, development and population, the result is greater stress to the Bay watershed ecosystem.

Urban Runoff

It has been shown that highways and road contribute a wide range of pollutants to ecosystems via urban runoff. Studies done in the 1980s in Rhode Island showed that state highways contributed 77% of the zinc, 66% of the lead, 39% of cadmium and 36% of copper inputs to the Pawtuxet River, a river that starts in the forests of central western Rhode Island but then winds through several miles of highly urbanized areas, crisscrossed by many roads and highways. 

Vehicle Emissions

Automobile and truck emissions contain compounds that increase ground level ozone concentrations, high concentrations of which irritate the human respiratory system, especially in the elderly and the very young. The greater Rhode Island area does not meet federal standards for ozone. An ecological impact of vehicle emissions is on the Bay itself – emissions contain a form of nitrogen, a nutrient that increases eutrophication of marine waterbodies. While studies on nutrient loading from air deposition on the Bay have not been completed, the Long Island Sound estuary, in neighboring Connecticut and New York, receives over 24% of nutrients from air deposition. Another environmental impact of vehicle emissions is their contribution to the “greenhouse” effect in the Earth’s atmosphere.