Abstract
The wetlands in the Prairie Pothole Region and in the Great Plains are notorious for their sensitivity to weather variability. These wetlands have been the focus of considerable attention because of their ecological importance and because of the expected impact of climate change. Few models in the literature, however, take into account spatial variation in the importance of wetland drivers. This is surprising given the importance spatial heterogeneity in geomorphology and climatic conditions have in the region. In this paper, I use spatially-varying coefficients to assess the variation in ecological drivers in a number of ponds observed over a 50-year period (1961-2012). I included the number of ponds observed the year before on a log scale, the log of total precipitation, and mean maximum temperature during the four previous seasons as explanatory variables. I also included a temporal component to capture change in the number of ponds due to anthropogenic disturbance. Overall, fall and spring precipitation were most important in pond abundance in the west, whereas winter and summer precipitation were the most important drivers in the east. The ponds in the east of the survey area were also more dependent on pond abundance during the previous year than those in the west. Spring temperature during the previous season influenced pond abundance; while the temperature during the other seasons had a limited effect. The ponds in the southwestern part of the survey area have been increasing independently of climatic conditions, whereas the ponds in the northeast have been steadily declining. My results underline the importance of accounting the spatial heterogeneity in environmental drivers, when working at large spatial scales. In light of my results, I also argue that assessing the impacts of climate change on wetland abundance in the spring, without more accurate climatic forecasting, will be difficult.
Highlights
MethodsWetland count data were obtained from the Waterfowl Breeding Population and Habitat Survey (WBPHS), conducted annually since 1955 by the U.S Fish and Wildlife Service and the Canadian Wildlife Service
Wetlands in the Prairie Pothole Region (PPR) and the Great Plains (GP) region of North America occur in small depressions formed during the last glaciation
The effective range is far greater than the mean nearest neighbour distances among strata (x = 250 km; sd = 106.83), indicating that the drivers in pond abundance were correlated at a broad scale
Summary
Wetland count data were obtained from the Waterfowl Breeding Population and Habitat Survey (WBPHS), conducted annually since 1955 by the U.S Fish and Wildlife Service and the Canadian Wildlife Service. The WBPHS is a systematic stratified survey of breeding waterfowl and wetlands over a large section of the major waterfowl breeding areas in Canada and the United States of America (USA). Aerial inventories are corrected for visibility by using ground survey data that are conducted concurrently at a subsample of the aerial survey transects (for more details, see [37]). The total abundance of ponds in the survey area are subsequently derived from visually-corrected values. I used the total annual abundance of ponds for the strata associated with the Parkland, Prairie Pothole and Grassland Regions (Fig 1). I restricted the time period to 1961 through 2012 to ensure overlap between pond and annual weather data
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