Forests cover a third of the land surface and we rely on them for a wide range of wood and food products, as well as services like cleaning water and storing carbon. Forests are also key regulators of global climate because they recycle water back to the atmosphere for later rainfalls. In a review paper published on August 21, 2015 in the journal Science, researchers from Max Planck Institute for Biogeochemistry, Germany, and the Woods Hole Research Center, USA, summarize international research results on forest health and global change.
Since pre-industrial times, the area of forest has shrunk nearly 15%. It is currently decreasing at a rate of about 0.3% per year (an area equivalent to Germany every three years), due to logging and clearing that far exceeds the areas of re-growing or planted forests.
But there is increasing concern over how forests respond to other, less visible, human impacts caused by hunting, selective logging, invasive pests, air pollution, and climate change.
“Some forest functions may recover quickly, in years or decades, but others could take centuries to regain pre-disturbance levels. Many of these changes will have direct impacts on the services forests provide to people” says Susan Trumbore, lead author of the review.
Changes in forest condition are often used as a proxy for forest health. However, health is well-defined only for individuals – as the absence of disease.
Although many countries carry out assessments of forest condition, researchers have struggled for decades to create operational definitions of forest health.
For example, increased tree mortality may indicate a decline in forest health at a local scale, but dying trees play an essential role in forest regeneration and nutrient cycling and are therefore a necessary component of normal forest functioning.
“For larger spatial scales, assessments of forest health are difficult due to a lack of common benchmarks that define what is a “normal” forest condition.” highlights Paulo Brando, coauthor of the article.
Reports of increased tree mortality across the globe are causing concern, however we lack the tools to analyze how big the problem is and what is causing trees to die. The satellites monitoring changes in global forest cover are limited to 30 x 30 meter pixels, where the death of a single tree will almost certainly go un-noticed.
On the smaller scale, individual trees are monitored in permanent forest plots that track all trees in an area usually ranging from 400 to 2000 square meters. Most countries contributing to the FAO (Food and Agriculture Organization of the United Nations) global assessments of forest health maintain such plots, but since methods are not standardized, it is hard to spot and attribute trends in tree mortality across boundaries.
New tools, like LiDAR (Light Detection And Ranging), are becoming available to fill the gap between plot observations and satellite imagery of the whole globe.
“Once trends in mortality are detected, we need additional research to understand how and why trees die” says Henrik Hartmann, coauthor of the publication. Experiments at tree and ecosystem scale, embedded in a monitoring framework of forest condition, are required to develop mechanistic understanding that can predict which trees are most vulnerable and how the capacity for forests to regenerate may be affected.
“Without such an understanding we will not be able to predict the trajectory of complex forest responses to multiple stressors from local to global scales”.
Forests have been around longer than people, and have already experienced some dramatic events in Earth’s history. "Forests survived a wide range of environmental changes during the millions of years of their existence. They will probably prove resilient to rapid anthropogenic changes in climate and environment, but humans should still be concerned about changes in forest condition. After all, forests can live without us, but we cannot live without them." underscores Susan Trumbore.
Trumbore, S., Brando, P., Hartmann, H. (2015) Forest health and global change. Science Vol. 349 no. 6250 pp. 814-818, DOI: 10.1126/science.aac6759
Max Planck Institute for Biogeochemistry
Max Planck Institute for Biogeochemistry
Woods Hole Research Center, USA
http://www.bgc-jena.mpg.de - Webpage Max Planck Institute for Biogeochemistry, Jena, Germany
http://www.whrc.org/ - Webpage Woods Hole Research Center, Falmouth, MA, USA
http://www.sciencemag.org/content/349/6250/814.abstract - Link to the publication in Science
Susanne Héjja | Max-Planck-Institut für Biogeochemie
New plate adds plot twist to ancient tectonic tale
15.08.2017 | Rice University
Global warming will leave different fingerprints on global subtropical anticyclones
14.08.2017 | Institute of Atmospheric Physics, Chinese Academy of Sciences
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).
The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
16.08.2017 | Physics and Astronomy
16.08.2017 | Materials Sciences
16.08.2017 | Interdisciplinary Research