Na September, Pacific Northwest Research Station wepụtara ya akụkọ "Ịgbakọ Green na Green: Gịnị bụ ihe Urban Tree kwesịrị?". Emechara nyocha na Sacramento, CA na Portland, OR.
Geoffrey Donovan, onye na-eme nchọpụta nke ụlọ ọrụ nyocha nke PNW, kpebiri na osisi ndị a kụrụ n'akụkụ ndịda na ọdịda anyanwụ nke ụlọ Sacramento belatara ụgwọ ọkụ eletrik n'oge okpomọkụ site na nkezi nke $25.16. N'ime nnyocha nke abụọ na Portland, otu Donovan chọpụtara na osisi okporo ámá na-eto n'ihu ma ọ bụ n'akụkụ ụlọ gbakwunyere nkezi $ 8,870 na ọnụahịa ọrịre ya ma belata oge ya n'ahịa ihe fọrọ nke nta ka ọ bụrụ ụbọchị 2. Uru akụ na ụba ndị a wụsara na ihe ndị agbata obi: osisi agbataobi na-eto n'akụkụ aka nri nke ọha gbakwunyere nkezi nke $12,828 na ọnụ ahịa ọnụ ụlọ niile dị n'ime 100 ụkwụ.
Ị nwere ike ịgụ ihe ọmụmụ a n'uju Ebe a.