Logging destabilizes forest soil carbon over time

Chelsea Petrenko, a doctoral candidate at Dartmouth College, is lead author of a study showing that logging triggers the gradual release of the carbon stored in a forest's mineral soils. Credit: Dartmouth College

Logging doesn't immediately jettison carbon stored in a forest's mineral soils into the atmosphere but triggers a gradual release that may contribute to climate change over decades, a Dartmouth College study finds.

The results are the first evidence of a regional trend of lower carbon pools in soils of harvested hardwood forests compared to mature or pristine hardwood forests. The findings appear in the journal Global Change Biology Bioenergy. A PDF of the study is available on request.

Despite scientists' growing appreciation for soil's role in the global carbon cycle, mineral soil carbon pools are largely understudied and previous studies have produced differing results about logging's impact. For example, the U.S. Forest Service assumes that all soil carbon pools do not change after timber harvesting.

The Dartmouth researchers looked at how timber harvesting affects mineral soil carbon over 100 years following harvest in the northeastern United States, where soils account for at least 50 percent of total ecosystem carbon storage. Mineral soils, which underlie the carbon-rich organic layer of the soil, make up the majority of that storage, but are sometimes not included in carbon studies due to the difficulty in collecting samples from the rocky, difficult terrain. The researchers hypothesized that the mineral soil carbon would be lower in forests that had been harvested in the last century than in forests that were more than 100 years old. They collected mineral soil cores from 20 forests in seven areas across the northeastern United States and compared the relative amounts of carbon in the soil from forests that were logged five years ago, 25 years ago, 50 years ago, 75 years ago and 100 years ago.

The results showed no significant differences between mineral soil carbon in the older versus harvested forests. But there was a significant relationship between the time since forest harvest and the size of the carbon pools, which suggested a gradual decline in carbon across the region that may last for decades after harvesting and result in increased atmospheric carbon dioxide.

"Our study suggests that forest harvest does cause biogeochemical changes in mineral soil, but that a small change in a carbon pool may be difficult to detect when comparing large, variable carbon pools," says lead author Chelsea Petrenko) (formerly Vario), a doctoral candidate in the Graduate Program in Ecology and Evolutionary Biology and a trainee in Dartmouth's IGERT program for Polar Environmental Change. "Our results are consistent with previous studies that found that soil carbon pools have a gradual and slow response to \disturbance, which may last for several decades following harvest."

A previous Dartmouth study found that clear-cutting releases detectible amounts of carbon stored in deep forest soils, challenging the notion that burning woody biomass for energy is more carbon-neutral than fossil fuels. "Mineral soil, which is the most significant ecosystem carbon pool in temperate forests, should be studied more closely before the carbon neutrality of bioenergy from local wood in temperate forests is asserted," says Petrenko, whose research focuses on the biogeochemistry of warming ecosystems and the impact on climate change.

Source:  Dartmouth College

Solar activity impacts polar ozone

Scientists have been able to confirm, for the first time, the long-term implications of solar-driven electron impact on the upper middle atmosphere ozone. Credit: NASA

The increase in greenhouse gases explains, to a large extent, the rise in the average temperature of Earth. According to the research study published in Nature Communications today, the Sun affects middle atmosphere ozone with potential implications on smaller scale to regional, but not global, climate.

Humankind is responsible for the global warming of our climate by increasing the amount of greenhouse gases in the atmosphere. However, according results published today, fluctuations in the activity of the Sun impact middle atmosphere ozone, providing a potential link to regional scale climate variability. This climate variability is not a trend, like climate change, but rather year-to-year fluctuations following solar activity. "The detected ozone variation may in part help understand the alternation of local mild and cold winter seasons, as hints have been obtained in previous research that the ozone changes in the middle atmosphere may link as far as the surface of Earth and affect, among other things, polar wind streams," Finnish Meteorological Institute researcher Dr Pekka Verronen reflects.

The research team was able to confirm, for the first time, the long-term implications of solar-driven electron impact on the upper middle atmosphere ozone. The results showed strong effects in the polar latitudes. The amount of ozone at 70-80 km altitude was found to vary more than 30 percent during a solar cycle, a period of approximately 11 years. The ozone variation between the extremes of the Sun's activity is so great that it is likely to impact the temperature balance of the atmosphere. These temperature changes can in turn have an effect on atmospheric winds.

Electrons from space: Auroras and ozone loss

According to the research study conducted by the Finnish Meteorological Institute, University of Otago and the British Antarctic Survey, the electrons, similar to those behind the aurora, cause significant solar cycle variation in the polar mesosphere ozone. The amount of ozone is smaller when more electrons enter the atmosphere. "These results are only the first step but an important one, allowing us to better understand the long-term impacts of this type of solar activity, and its role in regional climate variability," says Dr Monika Andersson who lead the study at Finnish Meteorological Institute.

Earth's radiation belts are regions in near-Earth space that contain vast quantities of solar energetic electrons, trapped there by Earth's magnetic field. During magnetic storms, which are solar wind-driven, the electrons accelerate to high speeds and enter the atmosphere in the polar regions. In the atmosphere, the electrons ionize gas molecules, leading to the production of ozone-depleting catalyst gases. Based on currently available satellite observations, electron precipitation may, during solar storms lasting a few days, reduce ozone in the upper atmosphere (60-80 km) as much as 90 per cent on a momentary basis.

Source: Finnish Meteorological Institute

The Composite plane life cycle assessment shows lighter planes are the future

Boeing Dreamliner 787. Credit: Image courtesy of University of Sheffield

A global fleet of composite planes could reduce carbon emissions by up to 15 per cent, but the lighter planes alone will not enable the aviation industry to meet its emissions targets, according to new research.

The study, by the Universities of Sheffield, Cambridge and University College London, is the first to carry out a comprehensive life cycle assessment (LCA) of a composite plane, such as the Boeing Dreamliner 787 or Airbus 350, and extrapolate the results to the global fleet.
The LCA covers manufacture, use and disposal, using publicly available information on the Boeing Dreamliner 787 fuselage and from the supply chain -- such as the energy usage of the robots that construct the planes. The study compares the results to the traditional -- and heavier -- aluminium planes.

Emissions during the manufacture of composite planes are over double those of aluminium planes. But because the lighter aircraft use significantly less fuel, these increased emissions are offset after just a few international flights. Over its lifetime, a composite plane creates up to 20 per cent fewer CO2 emissions than its aluminium equivalent.

Professor in Advanced Materials Technologies at the University of Sheffield, Alma Hodzic, said: "This study shows that the fuel consumption savings with composites far outweigh the increased environmental impact from their manufacture. Despite ongoing debates within the industry, the environmental and financial savings from composites mean that these materials offer a much better solution."

The researchers fed the data from the LCA into a wider transport model to gauge the impact on CO2 emissions as composite planes are introduced into the global fleet over the next 25 years, taking into account other factors including population, economic prosperity, oil prices and speed of adoption of the new technology.

The study -- published in the International Journal of Life Cycle Assessment -- estimated that by 2050, composite planes could reduce emissions from the global fleet by 14-15 per cent relative to a fleet that maintains its existing aluminium-based configuration.

Professor in Energy and Transport at UCL, Andreas Schäfer, explains: "The overall emissions reduction for the global fleet is lower than the reduction for an individual plane, partly, because by 2050, not all the fleet will be of composite construction. New planes entering the fleet before 2020 could still be in use by 2050, but the faster the uptake of this technology, the greater the environmental benefits will be."

Dr Lynette Dray from the University of Cambridge added: "Given that global air traffic is projected to increase four-fold between now and 2050, changing the materials used could avoid 500 million tonnes of CO2 emissions in 2050 alone, a value that roughly corresponds to current emission levels."

Professor Hodzic commented: "The industry target is to halve CO2 emissions for all aircrafts by 2020 and while composites will contribute to this, it cannot be achieved by the introduction of lighter composite planes alone. However, our findings show that composites -- alongside other technology and efficiency measures -- should be part of the picture."

Source: University of Sheffield

Maintaining a reliable value of the cost of climate change

Car exhaust. Credit: © Wrangler / Fotolia

The term Social Cost of Carbon is a figure that puts a dollar value on the climate damages per ton of CO2 released, and is used by, among others, policymakers to help determine the costs and benefits of climate policies. In the latest issue of the journal Science, a group of economists and lawyers urge several improvements to the government's figure that would impose a regular, transparent and peer-reviewed process to ensure it is reliable and well-supported by the latest facts.

"By providing an estimate of the damages from an extra ton of CO2 emissions, the Social Cost of Carbon tells us how much money we should devote to mitigating emissions. It separates the efficient policies from the wasteful ones, and for this reason is an incredibly useful tool in devising climate policy," said Prof. Michael Greenstone, one of the authors of the analysis and the director of the Energy Policy Institute at the University of Chicago. "Having said that, every day we are learning more about the science behind climate change and the economic impacts it imposes. It's vital that policy keeps up as our knowledge evolves."

The researchers suggest that the value be updated routinely, specifically they recommend every five years to balance the need for incorporating the latest research with a thorough review process. Part of that process should entail a review by the National Academy of Science's National Research Council, they say, to allow outside experts to be part of the process and suggest changes. They also argue that a single Social Cost of Carbon estimate should be maintained and shared by all government agencies.

"Greenhouse gas emissions cause the same damage, regardless of whether they are emitted through car tailpipes or factory smokestacks, and no matter where in the world they come from," Greenstone said. "For this reason, one, consistently used and rigorously maintained estimate of climate damages is imperative to ensure our climate policies are providing the maximum benefits for the least costs."

William Pizer, the lead author of the study and a professor at Duke University, further emphasized this need.

"To ensure that value exists, it's important that we draw on the expertise of all government agencies, as well as independent experts in the field," Pizer said. "This level of high-quality collaboration and peer review would decrease the likelihood of political factors interfering with the process, and ensure we have the most robust Social Cost of Carbon."

The authors give an example of why such a consistent, collaborative and well-supported value is important. When the Social Cost of Carbon value used today, which was developed with a vigorous approach, is applied to the EPA's recent Clean Power Plan that limits emissions from existing power plants, the benefits of the rule vastly outweigh the damages. However, when applying a past value used by a single agency, the plan's benefits do not exceed the costs.

Additionally, Greenstone noted that the figure is not just a tool for policymakers. The courts, businesses and others use this figure to make important decisions on the impacts associated with climate change.

"The U.S. Social Cost of Carbon is becoming a focal estimate of the likely climate damages globally," Greenstone said. "It's critical that that we get this number right, because it will influence policy around the world."

Greenstone and some of his colleagues have initiated a larger project to determine an even more rigorously maintained cost of climate change at a global scale. "Our hope is that this ongoing research project will inform the periodic revisions of the Social Cost of Carbon that we advocate for in this Science article."

Source: University of Chicago

How pace of climate change will challenge ectotherms

Turtles sunning themselves (stock image). Turtles are ectotherms, one of many that will be threatened by climate change, researchers say.
Credit: © xoanon / Fotolia

Animals that regulate their body temperature through the external environment may be resilient to some climate change but not keep pace with rapid change, leading to potentially disastrous outcomes for biodiversity.

A study by the University of Sydney and University of Queensland showed many animals can modify the function of their cells and organs to compensate for changes in the climate and have done so in the past, but the researchers warn that the current rate of climate change will outpace animals' capacity for compensation (or acclimation).

The research has just been published in Nature Climate Change (Letters), written by Professor Frank Seebacher School of Biological Sciences and Professor Craig Franklin and Associate Professor Craig White from the University of Queensland.

Adapting to climate change will not just require animals to cope with higher temperatures. The predicted increase to fluctuations in temperature as well as to overall temperature would require animals to function across a broader range of conditions. This is particularly important for ectotherms, animals that rely on external sources of heat to control body temperature, and are therefore more influenced by environmental temperatures.

The research showed that many groups of ectotherms, which make up more than 90 percent of all animals, are able to change their physiological function to cope with an altered environment, but the rapid pace and fluctuations of human-induced climate change present serious challenges.

The researchers studied 40 years of published data to assess how biological functions change in response to a sudden fluctuations in environmental temperatures. They found that the physiological rates of ectothermic animals, such as heart rate, metabolism and locomotion, had already increased over the past 20 years with increasing average temperatures.

"It is important that animals maintain the right balance between the large number of physiological functions despite environmental fluctuations. An increase in temperature that leads to changed reaction rates can upset that balance and cause the decline of individuals and species," said Professor Seebacher. "For example, movement requires energy and oxygen to be delivered to muscles. However, if metabolism or the cardiovascular system can't cope with increased temperatures, animals can no longer move to forage, migrate or interact with each other.

"The overall trend in the last 20 years has been to increased physiological rates, and we predict that this would continue to increase with increasing temperature. "Even if animals are able to maintain the balance of their physiological functions in a warmer climate, increased metabolism leads to increases in the food resources needed and could upset the balance in ecosystems, particularly if predator and prey populations respond very differently to the environmental temperature change."

Source: University of Sydney

Cost of cloud brightening for cooler planet revealed

University of Manchester scientists have identified the most energy-efficient way to make clouds more reflective to the sun in a bid to combat climate change. Credit: © magann / Fotolia

Marine Cloud Brightening is a reversible geoengineering method proposed to mitigate rising global temperatures. It relies on propelling a fine mist of salt particles high into the atmosphere to increase the albedo of clouds -- the amount of sunlight they reflect back into space. This would then reduce temperatures on the surface, as less sunlight reaches Earth.
Clouds form when water droplets gather on dust or other particles in the air. Increasing the amount of salt particles in the atmosphere allows more of these water droplets to form, making the clouds denser and therefore more reflective.

A new paper, published in the journal Philosophical Transactions of the Royal Society A, has looked at four different ways of getting the particles into the sky, to compare how effective they may be. The researchers found that a technique called the 'Rayleigh Jet' proved to be best.

Named after Lord Rayleigh, who provided the theory, the technique relies on spraying a fine jet of water that breaks down into small droplets into the sky. The liquid droplets evaporate quickly, leaving behind just the salt particles.

These particles, say the paper's authors, could be generated from specially built ships that could travel the world's oceans spraying salt particles into the air where they then hang in the atmosphere for several days until they return to Earth as rain.

Previous studies have optimised the size of the salt particles needed to produce the best increase in cloud reflectance but haven't taken into account how much energy the technique would need and how much it would cost to operate. This new paper, by teams at the universities of Manchester, Washington and Edinburgh, tackled this question. The researchers tested each technique so there was an increase in reflection of 5%, a figure that would combat the predicted effects of increased carbon dioxide levels over the rest of this century. They then looked at how much energy each would consume.

The scientists say that the Rayleigh jet method could produce the desired effect using 30 megawatts of energy, about the same energy that two large ships produce.

Dr Paul Connolly, based in the School of Earth, Atmospheric and Environmental Sciences at The University of Manchester, said: "It can be incredibly energy intensive to propel water high into the atmosphere and the energy required had never really been tested before. Our paper optimises the salt particle sizes to produce the required change in cloud reflectance for the least energy cost. It is an important finding if these techniques should be needed in the future.

"I am not recommending that we use any of these techniques now, but it is important to know how best to use them should they become necessary. Should no progress be made to reduce CO2 levels, then geoengineering techniques, similar to this, might become necessary to avoid dangerous rises in global temperatures."

Source: Manchester University

Mapping reveals targets for preserving tropical carbon stocks

This is an image from the Peru-wide, high-resolution carbon map showing the effects of deforestation (blue; no more carbon remaining) into a region of ultra-high carbon stocks in the surrounding forest (red). You can see massive losses in the bustling city of Pucallpa (right side) and the thousands of small farmers spreading into the forest to the west of Pucallpa. Image courtesy of Greg Asner. Credit: Greg Asner

A new high-resolution mapping strategy has revealed billions of tons of carbon in Peruvian forests that can be preserved as part of an effort to sequester carbon stocks in the fight against climate change. Tropical forests convert more carbon from the atmosphere into biomass than any other terrestrial ecosystem on Earth. However, when land is used for agriculture, as a wood source, or for mining, carbon is often released into the atmosphere where it contributes to climate change. Tropical deforestation and forest degradation account for about 10 percent of the world's carbon emissions annually.

There remain major challenges to conserving the carbon that's stored in these tropical landscapes on a national and international scale. A team led by Carnegie's Greg Asner developed a new high-resolution approach for prioritizing carbon conservation efforts throughout tropical countries. Their findings are published the week of November 10 in the Proceedings of the National Academy of Sciences. The team of authors emphasized that the low cost of conducting their project means that the same approach can be rapidly implemented in any country, thereby supporting both national and international commitments to reduce and offset carbon emissions.

Many of the geographic details about the carbon that's stored in tropical forest ecosystems remain unknown. In order for people involved in conservation efforts to select new areas in which carbon stocks can be best protected and enhanced, detailed information on which areas would make the best targets for protection are necessary. This means understanding each landscape's climate, topography, geology, and hydrology.

Using advanced three-dimensional forest mapping data provided by the Carnegie Airborne Observatory (CAO), integrated with satellite imaging data, the team was able to create a map of carbon density throughout the 128 million hectare (320 million acre) country of Peru, at a resolution of one hectare (2.5 acres).

"We found that nearly a billion metric tons of above-ground carbon stocks in Peru are at imminent risk for emission into the atmosphere due to land uses such as fossil fuel oil exploration, cattle ranching, oil palm plantations and gold mining," Asner said. "The good news is that our high-resolution mapping was able to identify three strategies for offsetting these upcoming emissions."
The team determined that there are opportunities to establish additional protected areas in some lowland Amazonian regions of Peru, where they found very high carbon densities, as well as in the so-called sub-montane region, which exists between the lowland Amazonian and Andean highland regions. Together the lowland Amazonian and sub-montane forests offer about 30 million hectares for potential new protected forest areas, which may be able to store close to 3 billion metric tons of carbon.

"Research is necessary to determine the exact state of our forests," stated Manuel Pulgar-Vidal, Peru's Minister of Environment, "For that, the Carnegie Institution, with the support of the Peruvian Environment Ministry, has developed the first high-resolution map of Peru's carbon stocks. This new map provides the evidence needed to start negotiating in the carbon market at a bigger scale. Our government is also studying carbon stocks in the soil, and is doing a forest inventory, and we have a forest investment program. These initiatives will better prepare us to face changes in land use."
The team also asserted that there are further opportunities for offsetting future emissions by improving enforcement in areas that are already designated for protection of carbon stocks. According to their research, the majority of already protected carbon stocks exist only in 10 parks and reserves, and just four of these are fully enforced.

"Transitioning partially protected preserves to fully protected ones would help to counterbalance a great deal of the carbon that is expected to be lost due to land use in the near future," Asner said.

Source:  Carnegie Institution