Abstract
This study examines the possible impacts of real-world wind farms (WFs) on vegetation growth using two vegetation indices (VIs), the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), at a ~250 m resolution from the MODerate resolution Imaging Spectroradimeter (MODIS) for the period 2003–2014. We focus on two well-studied large WF regions, one in western Texas and the other in northern Illinois. These two regions differ distinctively in terms of land cover, topography, and background climate, allowing us to examine whether the WF impacts on vegetation, if any, vary due to the differences in atmospheric and boundary conditions. We use three methods (spatial coupling analysis, time series analysis, and seasonal cycle analysis) and consider two groups of pixels, wind farm pixels (WFPs) and non-wind-farm pixels (NWFPs), to quantify and attribute such impacts during the pre- and post-turbine periods. Our results indicate that the WFs have insignificant or no detectible impacts on local vegetation growth. At the pixel level, the VI changes demonstrate a random nature and have no spatial coupling with the WF layout. At the regional level, there is no systematic shift in vegetation greenness between the pre- and post-turbine periods. At interannual and seasonal time scales, there are no confident vegetation changes over WFPs relative to NWFPs. These results remain robust when the pre- and post-turbine periods and NWFPs are defined differently. Most importantly, the majority of the VI changes are within the MODIS data uncertainty, suggesting that the WF impacts on vegetation, if any, cannot be separated confidently from the data uncertainty and noise. Overall, there are some small decreases in vegetation greenness over WF regions, but no convincing observational evidence is found for the impacts of operating WFs on vegetation growth.
Highlights
The Great Plains, home to the USA’s wheat and corn production, has the richest onshore wind resources across the nation
There are some small decreases in vegetation greenness over wind farms (WFs) regions, but no convincing observational evidence is found for the impacts of operating WFs on vegetation growth
This study examines the possible WF impacts on vegetation growth using MODerate resolution Imaging Spectroradimeter (MODIS) ~250 m resolution vegetation indices (NDVI and Enhanced Vegetation Index (EVI))
Summary
The Great Plains, home to the USA’s wheat and corn production, has the richest onshore wind resources across the nation. There are still many critical knowledge gaps between WFs/ABL interactions and their impacts on agriculture that need to be filled in before such a statement can be made Understanding such interactions and detecting and quantifying the WF effects on the surface/near-surface microclimate and vegetation activity are of crucial importance for the sustainability and growth of renewable wind energy, as well as agriculture, in the U.S. When wind turbines (WTs) operate, their spinning rotor blades inevitably create turbulence, modifying surface-atmosphere exchanges of energy, momentum, and moisture, altering near-surface ABL profiles and processes. We conduct an extensive analysis of the satellite measured vegetation index (VI) and meteorological data over two WF regions to detect and quantify possible WF impacts on vegetation growth These two WF regions have been previously well studied, with significant local warming effects reported [8,9,10,11,12,13]. (iii) Is there a change in the plant seasonal cycle after the WF construction? If yes, which season displays the most significant impact?
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