New papers are being published month by month with remarkable rapidity, with each field measurement essentially constituting a new publishable finding. The findings are already challenging old norms. Dry upland forests were long assumed to be removing methane from the air through the action of a class of soil microbes called methanotrophs.
But work by Megonigal and others is showing tree emissions can diminish or possibly exceed that methane-scrubbing capacity. How did this effect, measured by Bushong in and noted informally by forestry scientists for generations, stay hidden so long? What everyone had missed is that the stems and trunks and leaves of trees are surfaces, too, and the gas can flow there as well.
No more. Much of the methane now found to be escaping from trees in such wet conditions is thought simply to be microbial methane pumped up and out as oxygen flows down to the roots. But Gauci and other scientists are finding many instances in which trees produce their own methane—sometimes from microbes in the heartwood or other tissues and in other cases from a remarkable direct photochemical reaction thought to be driven by the ultraviolet wavelengths in sunlight.
It might not seem so surprising to think of trees in Amazon forests as conduits for this gas, given that soggy soils, peat bogs, and other low-oxygen environments are the domain of microbes that generate this gas. But other studies have found trees generating substantial methane even in dry upland ecosystems—in some cases within the trunk of the tree , not the soil. Such findings have spurred even more work, and it seems that everywhere someone looks, the more consequential, and confounding, the picture becomes.
At every scale, from whole forests to clusters of similar trees in a forest to the dynamics in individual trees, the one constant is variation, said Megonigal, at the Smithsonian research center in Maryland.
Covey described forests where similar trees in similar soils have been measured with a fiftyfold difference in methane emissions. Some trees have been measured to be emitting methane near the base and absorbing it higher up the trunk.
Closer analysis has found that a single tree can be absorbing methane near the base through microbial processes and emitting it higher up the trunk. Adding another, perhaps hopeful, twist, it appears that some trees actually sop up methane.
The work has not yet been published, but was outlined last year at the European Geosciences Union meeting by Gauci, Pangala, and another colleague. The study surveyed methane flows in trees in wet and dry soils from Central America and the Amazon to Britain and Sweden. Trees in wet soils uniformly were net emitters of methane but those in drier conditions in some regions actually were net absorbers of the gas.
The reality for climate is more complicated. The Paris Agreement on climate change supports forest projects as a way to draw down carbon dioxide emissions that countries have so far failed to constrain at the source. Independent of climate diplomacy, countries around the world are working to accelerate forest conservation under a separate agreement, the Convention on Biological Diversity, to safeguard their value as home to vast arrays of species.
But the methane findings do highlight the importance of assessing the full range of climate impacts—for better or worse—of different forest and tree types in different regions. As with better understanding of forest ecology, this can then guide projects to maximize benefits and limit risks. In recent years, other studies looking at the full impact of forests on the climate system have illuminated how a CO2-centered focus can miss significant additional cooling benefits of forests and—in some regions and forest properties—significant warming effects.
He and other researchers said a clearer view can improve climate models and also help insure that programs centered on the climate value of forests are as effective as possible. In higher latitudes, the simple shift from light-reflecting open land to dark, rough-surfaced tree canopies can warm the local climate by absorbing more sunlight. Forests in the tropics are particularly valuable for local climate, cooling the air around them as their metabolic machinery results in enormous evaporation—and that also can result in more sun-blocking cloud cover and precipitation.
Other work has shown how a complicated array of volatile organic compounds emitted by trees react to create haze and clouds, influencing temperature and precipitation in a variety of ways. Research demonstrates that exposure to trees has a relaxing effect on humans, reducing stress and imparting a sense of well-being.
Hospital patients with a window view of trees recover faster than those without. Children with Attention Deficit Disorder ADD are better able to concentrate after time spent in outdoor green settings. Data show that apartment buildings with high levels of greenery had significantly fewer crimes than those without any trees.
A belt of trees feet wide and 50 feet tall can reduce highway noise by up to 10 decibels, reducing the sound volume by half. Densely planted trees can also block unsightly views. Active involvement in tree planting programs leads to a stronger sense of community and the promotion of environmental responsibility and ethics. Planting programs also project a visible sign of change and provide the impetus for other community renewal and action programs.
One tree can sequester or take in more than one ton of carbon dioxide in its lifetime. Planting trees and avoiding deforestation are key measures in reducing the human impact on global climate change. Learn more about how the National Wildlife Federation is helping wildlife survive a changing climate and protect our forests:.
A groundbreaking bipartisan bill aims to address the looming wildlife crisis before it's too late, while creating sorely needed jobs.
More than one-third of U. The National Wildlife Federation is on the ground in seven regions across the country, collaborating with 53 state and territory affiliates to reverse the crisis and ensure wildlife thrive.
Uniting all Americans to ensure wildlife thrive in a rapidly changing world. Plus, they give us clean oxygen to breathe! To eat, trees go through a process called photosynthesis. To do this, their leaves pull in carbon dioxide and water through tiny pores, called stomata, and use energy absorbed from the sun to turn the CO2 and H2O into sugars. What's interesting is that it takes about equal parts carbon dioxide to make that same amount of oxygen.
It takes six molecules of carbon dioxide to produce one molecule of glucose the sugar that the tree needs for its metabolism. During photosynthesis, the tree then releases six molecules of oxygen as a bi-product. The process of photosynthesis occurs in the green parts of the leaf and stem, called chloroplasts.
That means that trees do most of their work taking in carbon dioxide and releasing oxygen when their leaves are green, which is during the spring and summer. As fall arrives and leaves change color, they can no longer do photosynthesis.
Some trees with green stems are still able to do some synthesizing of carbon dioxide into sugars, mostly utilizing carbon dioxide that they give off themselves. Trees also utilize oxygen when they break down the sugars they have created during photosynthesis to use for energy. However, they release more oxygen than they use up, so that they provide enough oxygen for you and me to breathe.
You can truly make a difference even with small pollinator plots at your own Read More ». I had a brilliant idea this morning to make place cards with leaf etchings on them, and I tried it out.
0コメント