A study published in the latest issue of Science suggests that changes in climate have influenced the global carbon cycle. The evidence was gathered from the high latitudes in the Northern hemisphere, where the changes in the seasonal flux were most highly pronounced.
The researchers from Scripps Institution of Oceanography at UC San Diego observed changes in biodiversity and biomass, caused by migrating plants, which affected the exchange of carbon between land, oceans and the atmosphere. The scientists are convinced that human induced activities alone, such as burning of fossil fuels, cannot be held responsible.
Climatologists monitor strictly the carbon flux as it is one of the most clear indicators of the influence of increasing carbon emissions. The amount of carbon that can be absorbed by forests determines the outcome of most climate prediction models.
In general, carbon is absorbed by vegetation through the process of photosynthesis, and released back by it via respiration or plant decay. The amount of carbon, which is absorbed or released is greatly determined by the plants growing season and age.
Now, the study noted that this seasonal cycle has been changing rapidly over the past half a century. The authors of point out that this could only be possible if there were other, still unknown ecological changes, which occur in the ecosystems and cause more carbon to be absorbed as a response to the increased concentrations of the gas. This hypothesis is further supported by the fact that the northern latitudes are becoming much greener, with species migrating towards the poles to escape from the warmer temperatures.
According to one of the authors of the study, Heather D. Graven, these are only few of the known factors that could explain the recent change in the carbon cycle, but these are definitely not all.
The increased seasonal fluxes were noted after a series of continuous measurements gathered between 2009 and 2011, and compared with historical data from the period between 1958 to 1961. The measurements indicated an increase in carbon absorption with up to 60% during the plants’ growing season and at the same time a drop in carbon release with up to 50%.
We don’t yet know the exact influence this fluctuation in carbon exchange will have on the planet, but one thing is known for sure. Although forests are absorbing much more since the 1960s, the total of 2 billion metric tons per year is a small fraction of the 9 billion metric tons that humans pump into the atmosphere per year.