In the higher or northern latitudes (from London upwards, in the case of Europe), the winds they have calmed down due to climate change. This means that it is no longer blowing as it used to in boreal forests or temperate forests or grasses in the Northern Hemisphere. What effects can this have on vegetation and, consequently, on its role in mitigating climate change?
This calm caused by climate change affects when the leaves fall in a way comparable to how temperature or rainfall does
A study published in the Proceeding of the National Academy of Science (PNAS) warns that the lack of wind caused by climate change can delay the aging and fall of leaves in these latitudes. “The wind dries the leaves and carries them towards the senescence and fall typical of autumn. With less wind this effect decreases and may be one of the reasons for this slowdown ”, he says. Josep Penuelas, author of the article and researcher of the CSIC and from CREAF.
In fact, the work confirms that this calm caused by climate change affects the time of leaf fall in a way comparable to how temperature or rainfall do, the factors most controlled so far in phenological studies.
“With this study we warn that the dynamics of the winds should be introduced as soon as possible in the models that are being used throughout the world to measure the effects of climate change on the rhythms of nature,” adds Peñuelas.
The study has made it possible to carry out 183,448 phenological observations in 2,405 sites, long-term measurements of water steam, carbon dioxide and 34 years of satellite data that measure the greenness of the landscape. In addition, the interannual differences that have been experienced in these places during leaf fall (autumn phenology) have been compared.
Winds, key in the carbon cycle
Right now, the Calm down of the winds seems to have positive effects on the net production of forests and vegetation, a positive fact to mitigate climate change, since the more the green grows, the more CO2 it withdraws from the atmosphere to produce trunks, branches and leaves.
Decreased winds reduce evapotranspiration, resulting in less water loss from the soil and consequently more favorable growing conditions in late fall
For one thing, the longer plant leaves are, the longer they photosynthesize. On the other hand, the work shows that the decrease in winds reduces evapotranspiration, which translates into less loss of water from the soil and, consequently, in more favorable growing conditions in late autumn. In addition, with less wind there is less cooling of the leaf surfaces and could therefore reduce frost damage.
In fact, the undeveloped lands of the northern high latitudes (> 50 °) are currently a large carbon sink, but they have experienced a significant increase in air temperature. For this reason, in these ecosystems the annual net productivity has increased year after year, among other reasons because spring has come early and the leaves now fall from the trees later.
However, experts warn that future weather may be more variable, with greater changes in temperature and rainfall. “Predicting how wind speeds will change with a changing climate remains challenging, but evidence suggests that wind speeds will be more extreme in various regions, even as annual mean speeds continue to decline. The combination of extreme and chronic winds would have a significant impact on plant growth, and these consequences for regional and global carbon sequestration could become negative and as important as those derived from variations in temperature and precipitation ”, he warns Peñuelas.
The research has led to an improved algorithm useful in models that predict the evolution of the carbon cycle and draw a totally opposite scenario towards 2100, where the fall of the leaves could come forward again giving a snowball effect (or positive feedback) that would exacerbate climate change itself.
Chaoyang Wu et al. “Widespread decline in winds delayed autumn foliar senescence over high latitudes” PNAS
Rights: Creative Commons.