A team of NASA and university scientists have found that Northern latitudes are starting to see lusher plant growth as a result of warmer average temperatures lengthening the growing seasons. The 30 year study examined the relationship between changes in surface temperature and vegetation growth between latitudes of 45°N and the Arctic Circle, and found these far Northern regions are becoming more and more like areas further South.
As the Northern latitudes get warmer, sea ice and snow cover melt sooner, so that they cover the surface for a shorter time each year. With the ground exposed for longer, with more available water, plants have a longer growing season leading to a general greening of the area and disruption of existing ecosystems. Ranga Myneni of Boston University’s department of Earth and Environment, and his colleagues, used satellite data to quantify vegetation changes at different latitudes between 1982 and 2011.
Because of the enhanced warming and longer growing season, large parches of vigorously growing vegetation now covered an area of more than 9 million square kilometers – a third of the Northern landscape, roughly equivalent to the entire United States. The area resembles what was found 400 – 700 kilometers to the South back in 1982. This growth is visible on the ground as an increasing abundance of tall shrubs and trees, and is most pronounced in Eurasia.
The change is being driven by what scientists call an amplified greenhouse effect. As the number of plants increase, they allow a region to absorb more solar radiation than the white snow which was there before, which warms the area further. This causes more snow and ice to melt, exposing the dark water and ground causing even more warming and permitting more plants to grow. It is feared that as the ground thaws, increased bacterial activity in the soil will release significant amounts of carbon dioxide and methans, adding to the burden of greenhouse gases.
The good news is that this new growth will eventually slow down and stop, since more plants means more fertile ground for pest infestations, forest fires. Summertime droughts will also limit growth.