Cities as environments

Abstract

makes suggestions for veg in semiarid cities reviews work on designs of cities, incl. Frederick Law Olmsted in developed nations, 80% of people live in cities; in poorest nations, only 20% live in cities; by 2000, 50% of population of world will live in cities use LA as an example: characterisitics of a semi-arid city-- consdiering the environment, heat island effect, water and soil, and city's ecological functions cities are usually located in key environemtns- on rivers, ocean harbors; therfore, major cities tend to develop at locatiosn crucial for biological conservation... need to designate wilderness areas and rural nature preserves veg is the key to making cities pleasant urban park movement in 19th cetury Heat island effect Cities are warmer than surrounding areas, b/c of increased heat production (caused by burning fossil fuels and other idustrial/residential activieies) and b/c there is a decreased rate of heat loss (there is less water avaialbe at the surface for evaporative cooling). COncreate, asphalt, and roofs tend to act as solar collectors and quickly emit heat. jin U.S. , average observed increase in temp in urban areas is ~1-2oC in winter and .5-1.00C in summer helps ozone production Water and soil in urban environment cities may have higher local rainfall than their surounding b/c dust above a city provides praticles for condensation of raindrops. Some urban areas have 5-10% more precipietation and conserably more cloud covera nd gog than do surrounding areas California's cities use 15% of water used in state; much of water use goes to ag, esp. cotton, rice, alfalfa, and other crops goes through different ecotypes would expect to see in LA basin; rare and endangered plants; urban conservation corridors (incl. that greenways could provide structure to sprawl) Olmstead believed using "greenswards" or lawns, "based on styles that had developed in the rainy climate of England, was inapproprtate for the Mountain States and California. The semi-arid American WEst called for devleopment of a new style of landscape design. cost of irrigation of large areas to secure good turf too expenseve, plus he would have rather emulated natural scenery and climate conditions urged use of veg that wouldn't require a lot of watering (14): "Olmested proposed thtat irrigated lawns in the American West be thought of as communal possessions that served civic functions rather than as a normal part of private poerties that met onlyh the needs of individual land owners" His principles of semi-arid design [are they ecological?-ng] leave as littlbe bare gorund exposed to view as possible by planting veg; arrange heavily visited places so that veg in and near them can be easily watered, assuring that dust and dryness is ketp to aminimum; plant vegetation so that it frames the distant vistas and obscures the dusyt middle distance common in semiarid environemtns; and fourth, to platnsas much veg on or around building to connect them visually ot the surrounding countryside Present vegeattion options: eliminate as much veg as possible polant only xerophytic vegetation vegetation lanted univformly (and thereofre water made availabe uniformly for veg irrigation ) per unti are of the city veg includes types that require moderate- and high-water availabilty but these corruing in limtied areas, so that the total water use approximates that of Option 3, but with the water and ve use perunit area varying spatialy allow unrestricted planting of all kind so fvegeattion, including veg characteristic of high or omderate rainfall termpate environments the fourth provides greates benefit for biological conservation and human uses of land