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COMMON GROUND VOL , 10 NO . 4 MAY /DUNE 1999 ® + ` °aa"• ' s � ih ). "y" �'.aQic++, '+t.7 • ..5 '• �..t ' '-j�'� :W - ,�. E�"r _ r�'+'. i �`-��.. .F�i _ ',`tiiy' _ R• . +r'� _ }:' . _ 7 • T � AssessingSatellite images show that since 1973 the Using its CITYgreen® software ($ 700) , lower Chesapeake Bay watershed has been American Forests calculated that tree loss in Treeconverted from a predominantly forested the urban corridor resulted in a 19 % increase ecosystem to an area dominated by cities in runoff from major storms, an estimated Coverand rural areas sparsely covered with trees . 540 million cubic feet of water . Replacing the More than 1 . 9 million acres ( 17% of the 11 . 4 lost stormwater retention capacity would illion-acre region) were cleared of heavy cost $ 1 . 08 billion . The lost trees also would Loss m forest between 1973 and 1997, according to have removed 9 .3 million pounds of air pol- the " Chesapeake Bay Regional Ecosystem lutants annually, at a value of $24 million. Analysis " conducted by American Forests The report recommends a 40% tree cover (202 / 9554500, www . amerieanforests . org) . for urban areas, ranging from 15 % in down- The survey found no difference in the loss of towns to 50 % in suburbs . Rural areas should tree cover in the Baltimore-Washington cor- strive for 50 % tree coverage, the report said , ridor compared to outlying areas . American Forests developed its software The study used satellite imagery from to help communities analyze the value of 1973, 1985 and 1997 to analyze tree loss in trees and vegetation and incorporate the the southeast section of the watershed in findings uito land use plans . The group has Delaware, Maryland and Virginia . The conducted similar studies in Atlanta, Austin, group conducted a more detailed exarp ina- Fort Lauderdale and Milwaukee . It offers tion of the urban corridor from Baltimore to regional training workshops and technical Washington, D . C . support for the software . % of lower Chesapeake Bay watershed with high vegetation and tree canopy coverage of 50% or greater in 1973e 550 % in 1997e 38 . to Loss : 1 ,911 ,376 acres . • % of region with little tree cover (less than 20% tree cover) in 1973 : 35 . • % in 1997: 500 • Increase : 1 ,793, 098 acres . • Lbs . of air pollutants removed by tree cover in the Baltimore-Washington corridor in 1973a 43 million. • Lbs . of air pollutants removed by tree cover in the Baltimore-Washington corridor in 1997e 34 million. • Avoided costs of pollutant removal by trees in 1997: $ 88 million. • Value of stormwater retention capacity of forest cover in the Baltimore-Washington corridor in 1973 : $5 . 7 billion . • . Value in 1997: $4 . 62 billion . • Loss : $ 1 . 08 billion. I I " ' I I I " 111 " III " " I " I 11 " " 1 " I ' I I B i 8 - BL �L� �N ` HDt1DND8S 'll I H 1818 XDS Dd iNNIHU34 DNINUVId AiNM 33NVUD a I Q 9N I NNVld GILSEnbax NOUDRUH00 SSMICIV SNI1103 NIANdW ` WW 6 0 Z Z Z TVrA ` U01 .85T1TJJV ' D'O ' NaLONIHSVM OZZZ OUS ` 1S 1UGX N 0091 Et16F 'ON .LIWNHd (IIVd ROVISOd ' S ' n A ' ONOIL40Nd - NON