Forests Flourish On Human CO2
Forests and their soils are one of our planet's major sinks of biologically active carbon and contain the majority of Earth’s terrestrial carbon stock. Some climate change alarmists have said that the world's forest are in danger from the effects of climate change. Recent studies have shown increases in plant growth across many forest types. Now, a new paper in the Proceedings of the National Academy of Sciences reports that the increase in forest biomass is due to rising CO2 levels and warmer weather—in other words, trees love global warming whether human caused or natural.
That there has been a resurgence in forest growth over the past century in North America, Europe and parts of Asia has been widely reported but the source of this growth spurt has remained uncertain. For example, growth could be caused by normal recovery from unknown disturbances. Without knowing the history of a forest, it is impossible to clearly know why the treas are growing faster. Using a unique dataset of tree biomass collected over the past 22 years, collected from 55 temperate forest plots with known land-use histories, researchers found that recent biomass accumulation greatly exceeded the expected growth caused by natural recovery.
The PNAS Early Edition paper, “Evidence for a recent increase in forest growth ,” was written by Sean M. McMahona, Geoffrey G. Parkera, and Dawn R. Millera, all researchers associated with the Forest Ecology Group at the Smithsonian Environmental Research Center (SERC). The motivation for the research was described in the paper's introduction:
The movement of carbon in our atmosphere, oceans, and terrestrial ecosystems is critical to predicting how climate change may influence the natural systems on which humans rely. Changes in ecosystems can, in turn, feed back into global atmospheric cycles through evapotranspiration, net ecosystem CO2 exchange, and surface albedo and roughness, which complicates predictions about future climate states. Key evidence that global changes may affect the functioning of forests is shown in changes in forest biomass over time, which can have important implications for whether or not forests accumulate biomass at a rate that would alter current trends of atmospheric carbon cycling.
The forest stands examined ranged in age from 5 to 250 years allowing an evaluation of the sustainability of the growth increase. McMahona et al. also collected over 100 years of local weather measurements and 17 years of on-site atmospheric CO2 measurements that show consistent increases in line with globally observed climate-change patterns. Somewhat surprisingly, it was found that sequestration of atmospheric carbon into recovering forests can continue even for forests over 800 years old. The results of the study is captured in the plots below, Figure 2 from the paper.
Fig. 2. Accelerated growth of multiple-censused plots can be seen in (A) where plot censuses show increased biomass gain. Plot censuses (diamonds) are linked by lines. Plots that had only one census were used to estimate the ensemble curve and are plotted here in gray. (B) The observed versus expected annual biomass change (Mg ha-1 yr-1) with 95% confidence limits (lines) from posterior parameter values of the estimated Monod function. Across all plot ages, consistently higher than expected annual biomass growth can be seen. Even plots that have a below or expected level of biomass increase show other years with higher than average biomass increase.
Combined, these observations show that changes in temperature and CO2 that have been observed worldwide can fundamentally alter the rate of critical natural processes, something that is predicted by biogeochemical models. It also means that all of the changes are not necessarily bad. The three most important climate change related factors were increased temperature, increased growing season length, and increased atmospheric CO2 levels. How each of these factors affect forest growth were explained as follows.
- Increased Temperature. Temperature is critical to all metabolic processes involved in uptake, release, and storage of carbon. Rising temperatures, especially when coinciding with adequate precipitation and without resource limitation, can increase tree metabolic processes that, in turn, lead to higher biomass accumulation.
- Increased Growing Season. Higher temperatures are also correlated with longer growing seasons. A steady lengthening of the growing season has been documented worldwide, and even a shift in the seasonal phase of surface temperatures has been detected. Growing degree days correlate with the speed of forest recovery from pasture in the Amazon and increased plant growth in boreal forests.
- Increased CO2. Atmospheric CO2 can increase tree growth through carbon fertilization. Trees have shown species-speciﬁc increases in growth under elevated CO2, but nutrient and water limitation can slow growth. Measurements of CO2 from SERC match the increases observed from annual averages on Mauna Loa.
The SERC forest stands are similar in composition and climate to the secondary forests that cover the eastern United States. To accurately extend this analysis to other forest will require additional study, but extending conclusions to other northern (boreal) forests is not unjustified. This report comes on the heals of a report that showed the ocean continues to absorb large amounts of CO2, the amount actually increasing as atmospheric CO2 levels rise. This may be due in part to strange, jellyfish like creatures called thaliaceans, that absorb large amounts of carbon, carrying it to the ocean depths when they die.
Trees and jellyfish are not the only living organisms to prosper as CO2 levels rise. Blue crabs, lobsters, and shrimp all thrived in higher CO2 levels, according to the resluts of one experiment reported in Geology. It turns out that nature is quite capable of handling a rise in CO2 levels without the need for any geoengineering or histrionics from the IPCC.
This should really come as no surprise, Earth has spent more time since the Cambrian explosion of life, 540 million years ago, in hot house conditions and life has thrived. The present day ice house climate, with permanent polar ice and mountain glaciers, is really the exception not the norm for earthly climate (see “The Grand View: 4 Billion Years Of Climate Change”). If Antarctica and Greenland did melt it would only signal a return to normal, not the catastrophe so luridly described by anthropogenic global warming fanatics. Not that I think man's modest release of CO2 is capable of forcing an end to the Pleistocene Ice Age, far from it. Nature is what it is and forces much greater than anything humanity can yield will dictate Earth's future climate.
Northern boreal forests are flourishing.
The world's forests form a critical component of the terrestrial carbon cycle. Trees absorb carbon, store carbon, and release carbon through growth, life and eventual decomposition after death. The carbon cycle is constantly moving carbon through living things, the oceans, the atmosphere and even Earth's crust. Calculating the amount of carbon stored in forests can help scientists predict how much carbon could move between forests and the atmosphere.
The PNAS report authors summed up this way: “Identifying this rate change is important to research on the current state of carbon stocks and the ﬂuxes that influence how carbon moves between storage and the atmosphere. These results signal a pressing need to better understand the changes in growth rates in forest systems, which influence current and future states of the atmosphere and biosphere.”
Earth's forests seem to be flourishing on the extra CO2 human civilization has been pumping into the atmosphere. Forest lands are doing their part, along with the oceans, to absorb the natural plant food that is carbon dioxide. How ironic, that the IPCC's climate change alarmists could turn out to be harming nature instead of helping it. They may be standing in the way of nature growing a new garden of Eden.
Be safe, enjoy the interglacial and stay skeptical.