We have been doing it all wrong with how we study what the effect of climate change on our biodiversity will be, say Jonas Lembrechts from the University of Antwerp and an international team of ecologists. Their warning is published in the scientific journal ‘Global Ecology and Biogeography’.
It is common practice among ecologists: if you want to know the faith of biodiversity in a changing climate, you first link the distribution of species to the climate at that location. To accomplish this, you use climate models based on the network of weather stations across the world. For many organisms, however, it turns out this approach is unlikely to be valid.
Case in point: northern Scandinavia, where Lembrechts and his colleagues studied the relationship between the tundra vegetation and the local climate. They noted temperature differences of several degrees Celsius between these global weather station models (at 1.5 m in the air) and the temperature just below the soil surface, right there where these small tundra plants are growing.
“Especially in winter, the differences are mind-boggling”, Lembrechts explains. “When the local weather station shows average temperatures dropping far below minus 10 °C, plants at the soil surface could still be comfortably at around 0 °C, as the snow cover in the tundra acts like a blanket. Many organisms are thus blissfully unaware of extreme conditions like that.” Consequently, the distribution of most tundra species also relates more strongly to these soil than to air temperatures, the study shows.
“Interestingly,” Lembrechts adds, “this relationship was much stronger for small plant species like grasses, while it was not visible for trees.” The former indeed experience a much stronger mismatch between the temperatures they experience, and the climate reported from weather stations.
This information has important implications for the question how biodiversity will react to climate change. This reaction will not be linear, as has often been expected, as the temperatures at the vegetation level are driven by other factors, for example changes in snow cover. This uncertainty on how climate change will look there where it matters for biodiversity needs to be solved urgently if we want to be able to predict what will happen in the future.