Currie, DavidOstrovsky, Marsha2013-11-072013-11-0720032003Source: Masters Abstracts International, Volume: 42-06, page: 2096.http://hdl.handle.net/10393/26531http://dx.doi.org/10.20381/ruor-18230Human activities potentially threaten key ecological processes, or "ecosystem functions", mainly through the habitat conversion associated with urbanization and agriculture. Although ecosystem functions can clearly be disrupted in severely degraded systems, it is not clear how those functions vary along the entire gradient of human activity at scales most relevant to global environmental change. To address this question, I used two remotely sensed indices of ecosystem function, as measured by the normalized difference vegetation index (NDVI) and thermal infrared radiation (TIR), to derive estimates of primary productivity and evapotranspiration, respectively, at 1-km resolution across multiple vegetation types in southern Canada. After controlling for the variation in NDVI and TIR related to the climatic gradient, I related these indices to measures of anthropogenic activity (road density, extent of natural cover, and protected areas status). While NDVI and TIR are both strongly related to climate and vegetation type, much of the residual variation in NDVI (up to 67%) and TIR (up to 55%) is related to human activity. Ecosystems in areas of intense human impact are generally less productive and exhibit less water cycling (i.e., energy-transforming) efficiency, but I found no evidence of threshold effects in the response of ecosystem function to increasing human impact. Ecosystems in protected areas (parks and reserves) have significantly higher productivity and, to a lesser extent, higher evapotranspiration, which suggests increased solar energy-transforming capacity. These relationships are strongest at coarse spatial scales and are generally consistent within different vegetation types. The magnitude of these effects along the entire gradient of human activity is substantial.87 p.enBiology, Ecology.Environmental Sciences.Thesis