Learn about bridge eco-systems (with links to Parts 1, 2, 3) PART 4 ECOLOGICAL CONCERNS Welcome engineers, architectural designers, and interested colleagues to the fourth edition of five "Illuminating World of Bridges." (Editions 1 through 3 are linked below) Thank you for the many email responses, including requests for ecological systems and biodiversity coverage. Here it is! Issue #4 describes the "stressor" effect that increasing urbanization has on organisms —specifi