Anthropogenic water depletion outweighs climate change as a cause of wet grassland bird decline in Lake Neusiedl – Seewinkel National Park

Changes in hydrology pose one of the greatest threats to continental wetlands. As global climate warming can affect hydrology by directly altering the hydrological cycle or by increasing agricultural water demand, it is generally difficult to correctly attribute the effects observed at site-level to either driver. We attempted to disentangle the effects of local and global factors on the regional population trends of bird species that act as indicators of semi-natural wet grasslands. Using long-term bird survey data from Lake Neusiedl – Seewinkel National Park, we analysed the effects of near-surface air temperature, spring precipitation, groundwater levels and European population trends on breeding abundance. We found that groundwater levels were the strongest predictor of Northern Lapwing and Common Redshank abundance, while Black-tailed Godwit abundance was more closely correlated with its European population trend. During the study period, groundwater levels declined significantly, a trend that could not be attributed to changes in precipitation or the climatic water balance. This strongly suggests that anthropogenic water abstraction is the actual cause. High plot-level habitat quality mitigated the effects of groundwater levels on Lapwings and Redshanks, but not the effects of European population trends on Godwits. This study demonstrates that local factors can outweigh the effects of global warming in the conservation of wet grasslands. High habitat quality can buffer periods of temporarily unfavourable conditions, and this will become increasingly important as weather extremes become more frequent. Our findings emphasise the crucial role of effective governance in wet grassland conservation. • Groundwater levels main driver of population numbers for two out of three indicator species • Decrease in groundwater levels due to overuse rather than climatic factors • Plot-level habitat quality can temporarily mitigate the effects of low groundwater levels. • Effective governance is key factor in the conservation of wet grasslands.