Atmosphere and mature trees-Tree Facts at

Want to help save the world from climate change? Then grab some seeds, or some seedlings, and start planting trees like there's no tomorrow. That may sound like a lot of trees, but the Earth has room for their gnarled bows and branches. In a new study that excluded cities and agricultural areas, researchers found that the planet has nearly 3. The study shows where in the world these trees could be planted, and how much carbon they could store.

Crowther emphasised that it remains vital to reverse the current trends of rising greenhouse gas emissions from fossil fuel burning and forest destructionand bring them down to zero. One scientist even received death threats after writing a commentary that argued against planting trees to prevent climate change. Unger says she received death threats, and that some colleagues stopped speaking to her. They concluded that the net effect of VOCs from forests is to cool the global climate 4. So how and why do trees give off methane? Show Hide There are about Sex xxx sample movies trillion trees on the planet and they play a major role in producing the oxygen we all breathe. The bottom line, says Pangala, Atmosphere and mature trees that almost all trees can both emit and absorb methane.

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Trees absorb Atmosphere and mature trees, removing and storing the carbon while releasing oxygen back into the air. Atmosphere and mature trees the past 15 years maturre have been 3 forest fires from West Point Military Academy, each causing stored carbon levels to decrease in amount. The former two species generally occupy wet sites with poorly drained mineral or organic soils, while white spruce is the climatic climax species on sites that are drier and higher in nutrient content. March 23, They are adapted for life in environments where resources are low or water is scarce. This may allow fungal spores to gain admittance and attack the tree. The page may contain broken links or outdated information, ad parts may not function in current web browsers. See how Icelandic trees are making a Sexy naked colleege girls in this short film by Euforgen. Young vigorous trees are accumulating carbon as they grow while mature trees are not. There are about species of gymnosperm trees, [21] including coniferscycads Private rooms monthly rental ireland, ginkgophytes and gnetales ; they produce seeds which are not enclosed in fruits, but in open structures such as pine conesand many have tough waxy leaves, such as pine needles. Trees provide a canopy and habitat for wildlife Sycamore and oak are among the many urban trefs that provide Atmosphsre urban homes for birds, bees, possums and squirrels. Danske Videnskabernes Selskab.

This story originally appeared on Yale Environment and is part of the Climate Desk collaboration.

  • You've probably heard that trees produce oxygen , but have you ever wondered just how much oxygen one tree makes?
  • General Information Trees help our soil remain healthy by reducing soil erosion and by creating a soil climate suitable for microorganism to grow.
  • By on.

Kapur trees Dryobalanops aromatica in Malaysia avoid overlapping crowns as they grow, which creates a jigsaw-puzzle pattern when viewed from below. When it comes to fighting global warming, trees have emerged as one of the most popular weapons.

With nations making little progress controlling their carbon emissions, many governments and advocates have advanced plans to plant vast numbers of trees to absorb carbon dioxide from the atmosphere in an attempt to slow climate change. But emerging research suggests that trees might not always help as much as some hope. China aims to plant trees over an area up to four times the size of the United Kingdom.

California is allowing forest owners to sell credits to CO 2 -emitting companies, and other US states are considering similar programmes, which could motivate projects that establish new forests and protect existing ones.

The European Union is moving towards allowing countries to include forest planting in their plans to fight climate change; some nations in the bloc have also pledged billions of dollars to tropical forest programmes.

Many scientists applaud the push for expanding forests, but some urge caution. They argue that forests have many more-complex and uncertain climate impacts than policymakers, environmentalists and even some scientists acknowledge. Although trees cool the globe by taking up carbon through photosynthesis, they also emit a complex potpourri of chemicals, some of which warm the planet.

The dark leaves of trees can also raise temperatures by absorbing sunlight. Several analyses in the past few years suggest that these warming effects from forests could partially or fully offset their cooling ability. Such concerns have prompted vigorous debate among scientists about how forests in different regions have warming or cooling effects. And no researchers are suggesting cutting down existing forests or curtailing efforts to combat deforestation. But as governments, corporations and non-profit organizations advance ever-more ambitious programmes to slow climate change, some scientists warn against relying on forests as a solution to global warming until a better understanding emerges.

Researchers are involved in major campaigns to collect data using aeroplanes, satellites and towers in forests to sample the full suite of chemicals that trees emit, which can affect both climate and air pollution. At the same time, some researchers worry about publishing results challenging the idea that forests cool the planet. One scientist even received death threats after writing a commentary that argued against planting trees to prevent climate change.

The questions are multiplying as more scientists enter the debate. At the same time, increasingly dire warnings about climate change — and the potential for huge amounts of money to go towards planting forests — have made working out how trees affect climate a matter of urgency.

If tree-planting programmes work as advertised, they could buy precious time for the world to reduce its reliance on fossil fuels and replace them with cleaner sources of energy. Although the analysis relies on big assumptions, such as the availability of funding mechanisms and political will, its authors say that forests can be an important stopgap while the world tackles the main source of carbon emissions: the burning of fossil fuels.

The first inkling that plants suck CO 2 from the air dates back to the s, when Swiss pastor Jean Senebier grew plants under different experimental conditions. He suggested that plants decompose CO 2 from the air and incorporate the carbon, an idea corroborated by subsequent discoveries about the mechanisms of photosynthesis.

The rationale is that trees can lock up carbon in their wood and roots for decades or even centuries. The climate treaty known as the Kyoto Protocol allowed rich countries to count carbon storage in forests towards their targets for limiting greenhouse-gas emissions.

Later negotiations laid out a framework for enabling wealthy countries to pay poorer tropical countries to reduce emissions from deforestation and to increase carbon in forests.

Source: X. Song et al. Nature , — Such schemes required firm data on how much carbon is locked up in forests. In the past few decades, scientists have worked to create national estimates of carbon loss and gain from vegetation by studying field plots and by combing through satellite data.

Researchers have known for decades that tree leaves absorb more sunlight than do other types of land cover, such as fields or bare ground. This effect is especially pronounced at higher latitudes and in mountainous or dry regions, where slower-growing coniferous trees with dark leaves cover light-coloured ground or snow that would otherwise reflect sunlight. Most scientists agree, however, that tropical forests are clear climate coolers: trees there grow relatively fast and transpire massive amounts of water that forms clouds, two effects that help to cool the climate.

More-recent studies have branched out to include other ways in which forests can influence climate. As trees live, grow and die, scientists have learnt, they are in constant conversation with the air, swapping carbon, water, light and a bewildering array of chemicals that can interact with the climate.

Atmospheric chemist Nadine Unger, then at Yale University in New Haven, Connecticut, conducted one of the first global studies examining one part of this exchange: the influence of volatile organic compounds, or VOCs, emitted by trees. These include isoprene, a small hydrocarbon that can warm the globe in several ways.

It can react with nitrogen oxides in the air to form ozone — a potent climate-warming gas when it resides in the lower atmosphere. Isoprene can also lengthen the lifetime of atmospheric methane — another greenhouse gas. Yet isoprene can have a cooling influence, too, by helping to produce aerosol particles that block incoming sunlight. Unger ran an Earth-system model that estimated the effects of chemical emissions from forests.

Her results suggest that the conversion of forests to farmland throughout the industrial era might have had little overall impact on climate 3. As a corollary, Unger suggested that reforestation would also have uncertain climate effects. Trees in tropical and temperate zones emit huge quantities of isoprene that is not accounted for in most forestry schemes. She acknowledged that her study was a first step, and called for increased monitoring of forest chemicals and their atmospheric interactions.

The article, and especially the headline which Unger did not write , triggered a tsunami of complaints from researchers, who disputed the science and said the piece threatened to undermine years of research and advocacy. At metres high, the Zotino Tall Tower Observatory measures gases and aerosols above taiga forest in central Siberia. A similar tall tower in the Amazon makes measurements above the tropical rainforest. Unger says she received death threats, and that some colleagues stopped speaking to her.

Some scientists, however, agreed that it was important to look at the impacts of forest VOCs. A team led by Dominick Spracklen and Catherine Scott, atmospheric chemists at the University of Leeds, UK, ran a model that included how aerosols from forests can seed clouds, which reflect sunlight.

They concluded that the net effect of VOCs from forests is to cool the global climate 4. Unger, who is now at the University of Exeter, UK, and Spracklen are discussing using a common experimental design to try to resolve their differences. They and other researchers say that such studies are hamstrung by sparse data sets on forest emissions.

The latest findings are piling on even more complexity. Ecologist Sunitha Pangala at Lancaster University, UK, spent much of and in the Amazon rainforest, where she placed gas-measuring chambers around the trunks of more than 2, trees. Researchers had previously assumed that methane leaked into the air directly from the soil, where it is produced by microbes. The new work suggests that trees could be another conduit for that microbial methane, potentially explaining why more methane has been detected above tropical wetlands than has been measured emanating from soil alone.

In a study first published last October, Gauci and other colleagues added another wrinkle when they found both methane and nitrous oxide, also a greenhouse gas, leaking from trees in upland forests 6.

The global significance of these findings is still unclear. Pangala and Gauci both estimate that the cooling effect of trees taking up carbon greatly outstrips the warming from tree emissions of methane and nitrous oxide. But Kristofer Covey, an environmental scientist at Skidmore College in Saratoga Springs, New York, has found methane leaking from non-wetland trees in temperate forests 7 , and argues that such emissions could, in some places, diminish the climate benefits of trees more than researchers and environmentalists realize.

The recent explosion of results underscores the need for a full account of the impacts of forests, says Unger. Scientists who champion forests say that although more research is always good, existing results are mature enough to support the use of forests to fight climate change, especially given the urgency of the problem. Researchers are now turning to sophisticated computer models and using larger and more-comprehensive data sets to nail down exactly what forests in different places do to the climate.

In some cases, the results have been sobering. Last October, a team led by ecologist Sebastiaan Luyssaert at the Free University of Amsterdam modelled a variety of European forest-management scenarios 8.

The researchers concluded that none of the scenarios would yield a significant global climate impact, because the effects of surface darkening and cloud-cover changes from any added forests would roughly eliminate their carbon-storage benefits. To estimate the climate impact of planting forests in different parts of the United States, ecologist Christopher Williams at Clark University in Worcester, Massachusetts, is combining global satellite data collected over more than a decade with carbon-sequestration figures based on data from the US Forest Service.

He has found in preliminary work that adding trees to the US west coast and to regions east of the Mississippi River makes sense, climatically speaking. But albedo changes make forest planting in the Rockies and the southwestern United States a bad deal for the climate in most cases, because the conifers that thrive in those regions are dark and absorb more sunlight than do underlying soils or snow.

Getting planners to adopt such methods could prove challenging, however. Williams has found that some resist considering albedo effects, including representatives of companies hoping to sell carbon credits for forest projects. More data about the climate impacts of forests could come from long-term studies that track the gases and chemicals that trees emit and absorb. Researchers are using a metre tower in the Amazon to monitor carbon, water and other chemical fluxes over a roughly square-kilometre area of intact rainforest northeast of Manaus in Brazil.

A companion tower in Siberia does the same. Teams have erected smaller research towers to collect similar samples at hundreds of sites around the globe amid different types of forest; a tower in Norway, for example, will soon be the first in that country to start taking data in a forest. But many important areas have not yet been covered. Scientists who debate the climate impacts of forests are eager to get their hands on these data.

And even those who are firmly convinced that forest projects can fight climate change welcome the added rigour of more-comprehensive studies.

Ellis, for one, acknowledges that the analysis he co-authored 1 considered albedo effects only crudely; the team did not consider VOCs and methane emissions from trees. Griscom, B. Natl Acad. USA , — Pan, Y. Science , — Unger, N. Nature Clim. Change 4 , — Scott, C. Nature Commun. Pangala, S. Welch, B. Change Biol. Covey, K. II, Lee, X. Luyssaert, S.

This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Although the bark functions as a protective barrier, it is itself attacked by boring insects such as beetles. Smartphone tour. Tree growth occurs in specialized tissues referred to as meristems. This was done so future researchers would be able to locate our sites and do further research in the years to come.

Atmosphere and mature trees. The ultimate climate change FAQ

It's also important to remember that trees not only release oxygen but also consume carbon dioxide. However, trees perform photosynthesis during daylight hours.

At night, they use oxygen and release carbon dioxide. Share Flipboard Email. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Updated October 07, Here are some typical calculations:. Note there are three ways to look at the amount of oxygen produced:.

One type of calculation simply looks at the average amount of oxygen produced via photosynthesis. A second calculation looks at net oxygen production, which is the amount made during photosynthesis minus the amount the tree uses. A third calculation compares the net oxygen production in terms of gas available for humans to breathe. McAliney, Mike. The bark of other varieties of oak has traditionally been used in Europe for the tanning of hides though bark from other species of tree has been used elsewhere.

The active ingredient, tannin , is extracted and after various preliminary treatments, the skins are immersed in a series of vats containing solutions in increasing concentrations.

The tannin causes the hide to become supple, less affected by water and more resistant to bacterial attack. At least drugs come from plant sources , many of them from the bark of trees. The papery bark of the white birch tree Betula papyrifera was used extensively by Native Americans. Wigwams were covered by it and canoes were constructed from it.

Other uses included food containers, hunting and fishing equipment, musical instruments, toys and sledges. Trees create a visual impact in the same way as do other landscape features and give a sense of maturity and permanence to park and garden. They are grown for the beauty of their forms, their foliage, flowers, fruit and bark and their siting is of major importance in creating a landscape.

They can be grouped informally, often surrounded by plantings of bulbs, laid out in stately avenues or used as specimen trees. As living things, their appearance changes with the season and from year to year. Trees are often planted in town environments where they are known as street trees or amenity trees. They can provide shade and cooling through evapotranspiration , absorb greenhouse gases and pollutants, intercept rainfall, and reduce the risk of flooding.

It has been shown that they are beneficial to humans in creating a sense of well-being and reducing stress. Many towns have initiated tree-planting programmes. Latex is a sticky defensive secretion that protects plants against herbivores. Originally used to create bouncy balls and for the waterproofing of cloth, natural rubber is now mainly used in tyres for which synthetic materials have proved less durable. This is also used as an insulator, particularly of undersea cables, and in dentistry, walking sticks and gun butts.

It has now largely been replaced by synthetic materials. Resin is another plant exudate that may have a defensive purpose. It is a viscous liquid composed mainly of volatile terpenes and is produced mostly by coniferous trees. It is used in varnishes, for making small castings and in ten-pin bowling balls. When heated, the terpenes are driven off and the remaining product is called "rosin" and is used by stringed instrumentalists on their bows. Some resins contain essential oils and are used in incense and aromatherapy.

Fossilised resin is known as amber and was mostly formed in the Cretaceous to 66 million years ago or more recently. The resin that oozed out of trees sometimes trapped insects or spiders and these are still visible in the interior of the amber.

The camphor tree Cinnamomum camphora produces an essential oil [] and the eucalyptus tree Eucalyptus globulus is the main source of eucalyptus oil which is used in medicine, as a fragrance and in industry. Dead trees pose a safety risk, especially during high winds and severe storms, and removing dead trees involves a financial burden, whereas the presence of healthy trees can clean the air, increase property values, and reduce the temperature of the built environment and thereby reduce building cooling costs.

During times of drought, trees can fall into water stress , which may cause a tree to become more susceptible to disease and insect problems, and ultimately may lead to a tree's death.

Irrigating trees during dry periods can reduce the risk of water stress and death. Trees have been venerated since time immemorial. To the ancient Celts , certain trees, especially the oak , ash and thorn , held special significance [] as providing fuel, building materials, ornamental objects and weaponry. Other cultures have similarly revered trees, often linking the lives and fortunes of individuals to them or using them as oracles.

In Greek mythology , dryads were believed to be shy nymphs who inhabited trees. The Oubangui people of west Africa plant a tree when a child is born. As the tree flourishes, so does the child but if the tree fails to thrive, the health of the child is considered at risk. When it flowers it is time for marriage.

Gifts are left at the tree periodically and when the individual dies, their spirit is believed to live on in the tree. Trees have their roots in the ground and their trunk and branches extended towards the sky. This concept is found in many of the world's religions as a tree which links the underworld and the earth and holds up the heavens. In Norse mythology , Yggdrasil is a central cosmic tree whose roots and branches extend to various worlds.

Various creatures live on it. Icons are placed beneath it to be worshipped, tree nymphs inhabit the branches and it grants favours to the devout who tie threads round the trunk. Sacred groves exist in China, India, Africa and elsewhere. They are places where the deities live and where all the living things are either sacred or are companions of the gods. Folklore lays down the supernatural penalties that will result if desecration takes place for example by the felling of trees.

Because of their protected status, sacred groves may be the only relicts of ancient forest and have a biodiversity much greater than the surrounding area. It has been named Hyperion and is The oldest living tree with a verified age is also in California. It has been dated by drilling a core sample and counting the annual rings.

It is estimated to currently be 5, years old. A little farther south, at Santa Maria del Tule , Oaxaca , Mexico, is the tree with the broadest trunk.

The tree's trunk is far from round and the exact dimensions may be misleading as the circumference includes much empty space between the large buttress roots.

Wohlleben, Peter ; Flannery, Tim F. From Wikipedia, the free encyclopedia. For other uses, see Tree disambiguation. Perennial woody plant with elongated trunk. Further information: Forest.

Main article: Root. Main article: Trunk botany. Main article: Bud. Main article: Leaf. Further information: Plant reproduction , Pollination , and Seed dispersal. Main article: Seed. Further information: Evolutionary history of plants. Further information: nut fruit and fruit. Main article: Wood fuel. Main articles: Wood and Timber.

Main article: Bonsai. Main article: Tree shaping. Further information: Bark botany. Main article: Ornamental trees. Further information: Resin , Latex , and Camphor. Main article: Tree worship. Main article: List of superlative trees. Arboretum da Vinci branching rule Dendrology Dendrometry Exploding tree Fruit tree Multipurpose tree — a tree grown and managed for more than one output Tree climbing Tree house List of lists of trees.

The previous record holder was named Methuselah, with an age of 4, years measured in Bibcode : Natur. Smartphone tour. University of Miami: John C. Gifford Arboretum. Archived from the original on 20 April Retrieved 23 September Newton Ask a Scientist.

Archived from the original on Retrieved Silva Fennica. Echo technical notes. Retrieved 22 September August Archived from the original on 8 September Gyde University of Wisconsin. Trees: A Visual Guide. University of California Press. The stem. University of Miami.

Food and Agriculture Organisation. Retrieved 1 October Bruce Forest Canopies. Academic Press. Annual Review of Ecology, Evolution, and Systematics. Letters to Nature. Nature Publishing Group. Archived from the original PDF on USA Today. Plant diversity and complexity patterns: local, regional, and global dimensions: proceedings of an international symposium held at the Royal Danish Academy of Sciences and Letters in Copenhagen, Denmark, 25—28 May Danske Videnskabernes Selskab.

The Plant List. Retrieved 14 November The Gymnosperms. Functional Biology of Plants. John Wiley. Cronodon Museum. National Park Service. National Public Radio. BBC News. Retrieved 3 September Encyclopedia of Earth. Macaulay Institute.

The Forest Community. The diversity of tree species in the boreal forest is quite low, with black spruce Picea mariana , larch or tamarack Larix laricina , and white spruce P. The former two species generally occupy wet sites with poorly drained mineral or organic soils, while white spruce is the climatic climax species on sites that are drier and higher in nutrient content.

Balsam fir Abies balsamea is a dominant tree species in the eastern half of the biome. Taiga Biological Station. March 23, University of California Museum of Paleontology. University of Basel: Institute of Botany. Biomes of the World. Marietta College. The World Encyclopedia of Trees.

Lorenz Books. Swiss Federal Research Institute. Bibcode : Sci Trees for Life. New Phytologist. University of Connecticut. Signaling in Plants. June 1, Forest Science.

Archived from the original on January 5, Mangroves of Singapore. Trees: Their Natural History. Cambridge University Press. Journal of Experimental Botany. The American Naturalist. IAWA Journal. Biology 6th edition. Pearson Education. Forest Research. Annual Review of Plant Biology.

Tree Rings and Climate. Blackburn Press. Retrieved 17 July Handbook of Photosynthesis. CRC Press. Biology: Concepts and Applications. Cengage Learning. Arturo March The Kew Plant Glossary. In: Klaus Kubitzki general editor ; Karl U. Kramer and Peter S.

Springer-Verlag: Berlin; Heidelberg, Germany. PLoS Biology. University of Texas Press. Interactive Assessment Worksheets. Biology of Plants. How do the seeds disperse to form new plants? North American Terrestrial Vegetation. Nature Foundation, St. Martin Philosophical Transactions of the Royal Society. New Age International. Tree Biology. Royal Forestry Society. Canopy research in the twenty-first century: a review of arboreal ecology. Tropical Ecology.

Food and Agriculture Organization of the United Nations. Old Knobbley. Annamalai University. University of Jamaica. Dictionary of Forestry. Society of American Foresters. FAO: Forestry Department. BBC News: Health. Things Cooks Love.

Andrews McMeel. Alaska Wild Harvest. Wayne's Word. Tropical Forest. Stoven November Colorado State University Extension. Thai Food and Travel. Retrieved 16 May Upasi Tea Research Foundation. The Guardian. United States Environmental Protection Agency. Woodland Investment Management.

Appalachian Hardwood Manufacturers. Mental floss. The Bonsai Specialist. New Holland Publishers. Bonsai Masterclass.

Sterling Publishing Co. The Bonsai Identifier. Quintet Publishing Ltd. Cottage and Garden : 28— Dwell, LLC.

Pictures World. Tanneries, Description of the Tanning Process". The Healing Power of Rainforest Herbs. World Health Organization.

Orchid growing secrets. Dorling Kindersley. Greenspace initiative. Forestry Commission. Greening London. Mayor of London. Materials World. History of the Atlantic Cable and Undersea Communications. The Mandala Projects. Flavours and fragrances of plant origin.

The Celtic Connection. Oxford University Press. The Times of India. American Indian Student Academic Services. The Bible. New International Version. The Overstory. Retrieved 5 June The Gymnosperm Database. San Francisco Chronicle. Retrieved 1 July Tasmanian Giant Trees Consultative Committee. Archived from the original on 10 February Retrieved 19 March Height m : Trees portal. History of botany. Plant morphology glossary. Cell wall Phragmoplast Plastid Plasmodesma Vacuole.

Plant physiology Materials. Evolution Ecology. Agronomy Floriculture Forestry Horticulture.

How much can forests fight climate change?

This story originally appeared on Yale Environment and is part of the Climate Desk collaboration. There are many mysteries in the Amazon. Until recently, one of the most troubling was the vast methane emissions emerging from the rainforest that were observed by satellites but that nobody could find on the ground. Around 20 million tons was simply unaccounted for. She found that trees, especially in the extensive flooded forests, were stimulating methane production in the waterlogged soils and mainlining it into the atmosphere.

And she had discovered a hitherto ignored major source of the second most important greenhouse gas in the atmosphere. Nobody is arguing that trees are therefore bad for climate and should be cut down. Indeed, in most cases, their carbon storage capability easily outweighs their methane emissions. But in a world where corporations plant trees to offset their carbon emissions, we badly need to know if their numbers add up, or if they are undermined by the complex chemistry of trees and methane.

Forest scientists have long amused their students by cutting holes in tree bark and setting fire to gases hissing from the trunk. The first recorded measurements were made in , when Francis Bushong of the University of Kansas cut a campus cottonwood and found the gas coming off was 60 percent methane.

For a while, few forest researchers wanted to know. They were not keen to hear that trees might not be quite as good for the climate as they hoped. Similarly, climate scientists saw forests as absorbing methane, rather than releasing it. It only slowly dawned on anyone that trees might do both.

When Pangala, then also at The Open University, made her first measurements of trees emitting methane in the swamps of Borneo, she had the same experience. But the results kept coming. In , Pangala published the findings from her Amazon expedition, during which she had travelled its tributaries and flooded forests, taking measurements of methane from surface water, floating aquatic plants, soils, and the stems and leaves of almost 2, trees in 13 floodplain locations.

This was not trivial. Every hectare of flooded forests was emitting several kilograms of methane each day. The on-the-ground findings doubled previous estimates of Amazon methane emissions to around 40 million tons a year.

The trees were emitting as much methane as all the tundra ecosystems of the Arctic, whose permafrost contains huge amounts of the gas—a store that is expected to be released in ever-greater quantities as the region warms and its soils thaw.

It was a game-changer. She provided a full ecosystem picture, and showed the missing methane was coming from trees. It was very difficult to argue with. He had pointed out in that remote sensing data from satellites suggested the Amazon was emitting twice as much methane as researchers on the ground could account for.

Now the world knew why. After water vapor and carbon dioxide, methane is the most important greenhouse gas. In fact, molecule for molecule, it is a much more potent planet-warmer than CO2. Human sources—most prominently rotting landfills, coal mines, rice paddies, cattle, and leaks from natural gas pipelines—have raised atmospheric concentrations by around percent.

They are reckoned to be responsible for around a fifth of global warming. Because methane only lasts in the atmosphere for around a decade, removing major sources could have a quicker effect on global temperatures than removing CO2, which lasts for centuries. Far from it. The numbers are too high. The most intense tree emissions are almost certainly from forested areas of tropical wetlands, such as the Amazon. But the role of trees outside wetlands cannot be discounted.

Likewise, trees outside the tropics do not generally emit on the scale of those in the tropics. Temperatures are too low. But even so, some forests in the mid-latitudes may at times emit enough methane to negate the methane-absorbing capacity of their soils, turning their ecosystems from net methane sinks to net sources, says Megonigal. So how and why do trees give off methane?

But what role? Some researchers see wetland tree trunks merely as passive conduits for methane generated by micro-organisms in the waterlogged soils. Tree trunks may look solid, but they contain spaces and channels through which gases travel up and down. But it seems that wetland trees are much more than conduits. They also create the conditions, and provide the raw materials, for methane generation by micro-organisms.

Many trees, especially outside wetlands, also actively generate methane. Some methane comes from photochemical reactions in their foliage. More may be from microbes living in the trunks that themselves generate methane, says Gauci. Some researchers have termed trees as crypto-wetlands or vertical wetlands. The scale of these processes remains unclear. But what we are learning, says Covey, is that the chemical interactions between trees and the atmosphere are extremely dynamic.

Not all of that action is bad news. For as well as emitting methane, trees also absorb the gas. Indeed, the same tree may be a net source or sink depending on the season, its age, or even which bit of the tree you are talking about. Many emit methane close to their base while absorbing it further aloft. The bottom line, says Pangala, is that almost all trees can both emit and absorb methane. But finding out the net balance is very hard because it changes so much.

And that methane is, of course, only part of a much bigger picture of the role of trees in climate. Her former supervisor at The Open University is on the case.

Gauci currently is working on the Indonesian island of Sumatra with the owners of huge plantations of acacia trees growing on drained peat bogs. Dried peat emits carbon dioxide, and to prevent that, the Indonesia government is requiring peatland concession holders to plug drains and raise the water table. But the risk, says Gauci, is that rising waters will trigger a burst of methane emissions from the waterlogged trees.

The need is all the greater, notes Covey, when governments and corporations are planting trees with the promise that they will thereby offset their industrial emissions by adding trees that soak up CO 2 , thus meeting their international obligations for cutting greenhouse gas emissions.

But that still requires a lot more science, and a lot more data. Earlier this month, Pangala, now at Lancaster University, flew to Mexico with her young son, ready to clamp methane monitoring equipment to mangroves in the coastal swamps of the Yucatan. There are snakes to contend with. But it is wet and there are trees.

So surely they will be releasing methane. The only question is how much. Andy Greenberg and Excerpt. Alex Davies. The Glory and Terror of the Quantified Baby. Garrett M. Sign up for the Backchannel newsletter. Featured Video. Topics Climate Desk methane Climate Change. Daniel Oberhaus. Marcus Woo. Matt Simon.

Can We Plant 20 Million Trees for ? The Math Says Yes. Rhett Allain. Adam Rogers. Charles Graeber.