Climate Change Is Also Destroying Forests In The North

2021-02-24   |   by CusiGO

Climate change is destroying forests in the northern hemisphere. Whether in the United States or Eurasia, the response of forests to warming is almost crazy. As the temperature rises, the expansion to higher latitudes is common and will continue until the end of this century. But at the same time, the increase in heat also makes trees more vulnerable to their usual enemies fire, wind and pests.

In principle, the amount of carbon dioxide that trees need to grow is very good. On the one hand, the warming they produce prolongs the time and speed of growth. The more carbon dioxide there is in the atmosphere, the higher their emission rate. At the individual level, it means a faster life cycle. At the specific forest level, it involves its expansion, increasing density (more units per area) or forest area. However, all of this depends on the type of forest. In the Mediterranean, for example, carbon dioxide is inefficient due to its high fertilizer efficiency and water shortage. In the northernmost region, temperature is the most important.

A study led by Spanish scientists analyzed the evolution of the northern forest boundary, To do this, they measured tree ring growth in 37 locations in the northern hemisphere (plus the Andes) since 1950 and compared it with climate change, especially temperature and precipitation. “The evolution of halo width is related to temperature,” explains Jesus Julio barter, a researcher and Research Coordinator at the Pyrenees Ecological Institute (ipe-csic).

They found that, especially since the 1980s, almost all of the 20 species analyzed have accelerated their growth. This is consistent with the increase of global warming. In addition, climate change extends summer exactly where summer is shortest. The growth period of forests in Scandinavia, northern Canada or the Alps is limited to June and July. But it doesn’t stop growing, and they estimate that trees can enjoy twice the growth time.

The authors of the study, published in global change biology, used the data to simulate how the northern end of the forest would move as carbon dioxide emissions increased. In the most pessimistic scenario, after 2050, scientists worry that forest growth and expansion will be decoupled from warming. “In the 21st century, trees may not respond as they used to, they may not work as thermometers,” the waiter hopes.

Another striking phenomenon is the unequal effect of climate change on the age of trees. In North America, they just found that trees in the East are more prolific and produce more seeds than trees in the West. The only explanation they found was that warming had a greater impact on young forests than on forests.

“This explains the division between the East and the West; most trees in the East are young and grow rapidly, reaching the level of increasing fertility, so any indirect effect of climate that stimulates their growth will also increase seed production.”, James S. Clark, Professor of environmental science at Duke University and co-author of the study, explained in a note. “We see that the largest and oldest trees in the West are just the opposite. Of course, there are small trees and big trees in both areas, but their size structure is very different and they react in different ways. The problem is that the forest landscape in North America may change fundamentally in the future.

In Europe, a newly published paper studies the impact of climate change on forest vulnerability. Forests face three common enemies (except humans): fire, wind and pests. With the support of the Russian ural Ireland forest satellite and the database of three types of events since 1978, scientists have established the European forest vulnerability index, My understanding is how much forest biomass may be lost if such disturbance occurs. Then they linked it to the weather.

In absolute terms, the biggest dangers are still fire and temporary wind, but over the past 40 years, pest exposure and vulnerability have grown faster than the other two threats. The authors estimate that nearly 60% of the forest biomass in Europe (about 2 million square kilometers, accounting for one third of the European soil) is vulnerable to wind, fire, pest or their combination.

Giovanni Forzieri, a researcher at the joint research center (JRC) of the European Commission and lead author of the study, explained in an email: “this increase in vulnerability seems to be mainly driven by temperature rise, which is the leading factor in 91% of the region.”. On the one hand, the temperature generally increased, on the other hand, the effect of heat on pest exposure can explain this trend. Around 2000, this process seems to be more obvious, with the thermal anomaly as high as 0.5% compared with the average value from 1970 to 1990. “This shows that around 2000, the temperature reached a turning point, greatly changing the forest’s resistance to pest outbreaks,” Forzieri detailed.

The study, published in nature letters, also found edge effects. “Cold climate forests in Finland, northern Russia and the European Alps, as well as warm and arid forests in the hinterland of the Iberian Peninsula, are particularly vulnerable ecosystems. “They are characterized by high overall vulnerability, which is exacerbated by climate change,” the JRC scientists concluded.

“There will be areas, such as colder areas, that will be favored by climate change,” said Raul s รก nchez Salguero, a forestry researcher at the University of Pablo de olavide and co-author of the first study. But in other areas, such as the Mediterranean basin, constraints will accumulate. For him, “there may be other forests, but there are no more.”

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