Concentrations of atmospheric carbon dioxide (CO2) increased at "record-breaking" speed last year, according to the World Meteorological Organization's (WMO) annual Greenhouse Gas Bulletin released Monday.
According to the report, concentrations of CO2 reached 403.3 parts per million in 2016, up from 400.00 parts per million the year prior. This acceleration was due to a strong El Niño event—which triggered droughts and reduced the capacity of forests, vegetation and the oceans to absorb CO2—as well as human activities, such as the burning of fossil fuels.
"The last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago, the temperature was 2-3°C warmer and sea level was 10-20 meters higher than now," a press release for the bulletin stated. "Concentrations of CO2 are now 145% of pre-industrial (before 1750) levels."
Methane and nitrous oxide—the two other main greenhouse gases—also hit record levels in 2016.
"Population growth, intensified agricultural practices, increases in land use and deforestation, industrialization and associated energy use from fossil fuel sources have all contributed to increases in concentrations of greenhouse gases in the atmosphere since the industrial era, beginning in 1750," the release continued.
This rapid surge in greenhouse gases could trigger unprecedented climate change and lead to "severe ecological and economic disruptions," the report said.
In light of the bulletin, WMO Secretary-General Petteri Taalas called on international governments to drastically reduce greenhouse gas emissions.
“Without rapid cuts in CO2 and other greenhouse gas emissions, we will be heading for dangerous temperature increases by the end of this century, well above the target set by the Paris climate change agreement. Future generations will inherit a much more inhospitable planet," said Taalas. "CO2 remains in the atmosphere for hundreds of years and in the oceans for even longer. The laws of physics mean that we face a much hotter, more extreme climate in the future. There is currently no magic wand to remove this CO2 from the atmosphere."
The WMO report comes before the United Nations Environment Program releases its separate Emissions Gap Report on Oct. 31, which tracks the policy commitments made by countries to reduce emissions and how these policies compare to the goals set by the United Nations Framework Convention on Climate Change (UNFCCC).
Last year's UN Environment report had already urged the world to "urgently and dramatically" cut a further 25 percent from predicted 2030 emissions to minimize dangerous climate change. That's not to mention that the world's efforts to curb climate emissions have been drastically impinged by President Donald Trump's controversial decision to withdraw the U.S.—one of the planet's largest single emitters of greenhouse gases—from the Paris agreement.
"The numbers don't lie. We are still emitting far too much and this needs to be reversed," Erik Solheim, the head of the United Nations' environment program, said. "The last few years have seen enormous uptake of renewable energy, but we must now redouble our efforts to ensure these new low-carbon technologies are able to thrive. We have many of the solutions already to address this challenge. What we need now is global political will and a new sense of urgency."
Here are the key findings of the Greenhouse Gas Bulletin:
Carbon dioxide: CO2 is by far the most important anthropogenic long-lived greenhouse gas. Globally averaged concentrations for CO2 reached 403.3 parts per million in 2016, up from 400.00 ppm in 2015. This record annual increase of 3.3 ppm was partly due to the strong 2015/2016 El Niño, which triggered droughts in tropical regions and reduced the capacity of “sinks" like forests, vegetation and the oceans to absorb CO2. Concentrations of CO2 are now 145 percent of pre-industrial (before 1750) levels.
The rate of increase of atmospheric CO2 over the past 70 years is nearly 100 times larger than that at the end of the last ice age. As far as direct and proxy observations can tell, such abrupt changes in the atmospheric levels of CO2 have never before been seen.
Over the last 800 000 years, pre-industrial atmospheric CO2 content remained below 280 ppm, but it has now risen to the 2016 global average of 403.3 ppm.
From the most-recent high-resolution reconstructions from ice cores, it is possible to observe that changes in CO2 have never been as fast as in the past 150 years. The natural ice-age changes in CO2 have always preceded corresponding temperature changes. Geological records show that the current levels of CO2 correspond to an “equilibrium" climate last observed in the mid-Pliocene (3–5 million years ago), a climate that was 2–3 °C warmer, where the Greenland and West Antarctic ice sheets melted and even some of the East Antarctic ice was lost, leading to sea levels that were 10–20 meters higher than those today.
Methane: Methane (CH4) is the second most important long-lived greenhouse gas and contributes about 17 percent of radiative forcing. Approximately 40 percent of methane is emitted into the atmosphere by natural sources (e.g., wetlands and termites), and about 60 percent comes from human activities like cattle breeding, rice agriculture, fossil fuel exploitation, landfills and biomass burning.
Atmospheric methane reached a new high of about 1,853 parts per billion (ppb) in 2016 and is now 257 percent of the pre-industrial level.
Nitrous Oxide: Nitrous oxide (N2O) is emitted into the atmosphere from both natural (about 60 percent) and anthropogenic sources (approximately 40 percent), including oceans, soil, biomass burning, fertilizer use, and various industrial processes.
Its atmospheric concentration in 2016 was 328.9 parts per billion. This is 122 percent of pre-industrial levels. It also plays an important role in the destruction of the stratospheric ozone layer which protects us from the harmful ultraviolet rays of the sun. It accounts for about six percent of radiative forcing by long-lived greenhouse gases.
By Melissa Gaskill
Two decades ago scientists and volunteers along the Virginia coast started tossing seagrass seeds into barren seaside lagoons. Disease and an intense hurricane had wiped out the plants in the 1930s, and no nearby meadows could serve as a naturally dispersing source of seeds to bring them back.
Restored seagrass beds in Virginia now provide habitat for hundreds of thousands of scallops. Bob Orth, Virginia Institute of Marine Science / CC BY 2.0<p>The paper is part of a growing trend of evidence suggesting seagrass meadows can be easier to restore than other coastal habitats.</p><p>Successful seagrass-restoration methods include <a href="https://www.sciencedirect.com/science/article/abs/pii/S0304377099000078?via%3Dihub" target="_blank">transplanting shoots</a>, <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1061-2971.2004.00314.x" target="_blank" rel="noopener noreferrer">mechanized planting</a> and, more recently, <a href="https://www.nature.com/articles/s41467-020-17438-4" target="_blank" rel="noopener noreferrer">biodegradable mats</a>. Removing threats, proximity to donor seagrass beds, planting techniques, project size and site selection all play roles in a restoration effort's success.</p><p>Human assistance isn't always necessary, though. In areas where some beds remain, seagrass can even recover on its own when stressors are reduced or removed. For example, seagrass began to recover when Tampa Bay improved its water quality by reducing nitrogen loads from runoff by roughly 90%.</p><p>But more and more, seagrass meadows struggle to hang on.</p><p>The marine flowering plants have declined globally since the 1930s and currently disappear at a rate equivalent to a football field every 30 minutes, according to the <a href="https://www.unep.org/resources/report/out-blue-value-seagrasses-environment-and-people" target="_blank" rel="noopener noreferrer">United Nations Environment Programme</a>. And research published in 2018 found the rate of decline is <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GB005941" target="_blank" rel="noopener noreferrer">accelerating</a> in many regions.</p><p>The causes of decline vary and overlap, depending on the region. They include thermal stress from climate change; human activities such as dredging, anchoring and coastal infrastructure; and intentional removal in tourist areas. In addition, increased runoff from land carries sediment that clouds the water, blocking sunlight the plants need for photosynthesis. Runoff can also carry contaminants and nutrients from fertilizer that disrupt habitats and cause algal blooms.</p><p>All that damage comes with a cost.</p>
The Value of Seagrass<p>As with ecosystems like rainforests and <a href="https://therevelator.org/mangroves-climate-change/" target="_blank">mangroves</a>, loss of seagrass increases carbon dioxide emissions. And that spells trouble not just for certain habitats but for the whole planet.</p><p>Although seagrass covers at most 0.2% of the seabed, it <a href="https://www.unenvironment.org/news-and-stories/story/seagrass-secret-weapon-fight-against-global-heating" target="_blank">accounts for 10%</a> of the ocean's capacity to store carbon and soils, and these meadows store carbon dioxide an estimated 30 times faster than most terrestrial forests. Slow decomposition rates in seagrass sediments contribute to their <a href="https://www.researchgate.net/publication/238506081_Assessing_the_capacity_of_seagrass_meadows_for_carbon_burial_Current_limitations_and_future_strategies" target="_blank" rel="noopener noreferrer">high carbon burial rates</a>. In Australia, according to <a href="https://onlinelibrary.wiley.com/doi/10.1111/gcb.15204" target="_blank" rel="noopener noreferrer">research</a> by scientists at Edith Cowan University, loss of seagrass meadows since the 1950s has increased carbon dioxide emissions by an amount equivalent to 5 million cars a year. The United Nations Environment Programme reports that a 29% decline in seagrass in Chesapeake Bay between 1991 and 2006 resulted in an estimated loss of up to 1.8 million tons of carbon.</p>
Eelgrass in the river delta at Prince William Sound, Alaska. Alaska ShoreZone Program NOAA / NMFS / AKFSC; Courtesy of Mandy Lindeberg / NOAA / NMFS / AKFSC<p>Seagrasses also protect costal habitats. A healthy meadow slows wave energy, reduces erosion and lowers the risk of flooding. In Morro Bay, California, a 90% decline in the seagrass species known as eelgrass caused extensive erosion, according to a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0272771420303528?via%3Dihub" target="_blank" rel="noopener noreferrer">paper</a> from researchers at California Polytechnic State University.</p><p>"Right away, we noticed big patterns in sediment loss or erosion," said lead author Ryan Walter. "Many studies have shown this on individual eelgrass beds, but very few studies looked at it on a systemwide scale."</p><p>In the tropics, seagrass's natural protection can reduce the need for expensive and often-environmentally unfriendly <a href="https://www.nioz.nl/en/news/zeegras-spaart-stranden-en-geld" target="_blank" rel="noopener noreferrer">beach nourishments</a> regularly conducted in tourism areas.</p><p>Seagrass ecosystems improve water quality and clarity, filtering particles out of the water column and preventing resuspension of sediment. This role could be even more important in the future. By producing oxygen through photosynthesis, meadows could help offset decreased oxygen levels caused by warmer water temperatures (oxygen is less soluble in warm than in cold water).</p><p>The meadows also provide vital habitat for a wide variety of marine life, including fish, sea turtles, birds, marine mammals such as manatees, invertebrates and algae. They provide nursery habitat for <a href="https://wedocs.unep.org/bitstream/handle/20.500.11822/32636/seagrass.pdf?sequence=1&isAllowed=y" target="_blank" rel="noopener noreferrer">roughly 20%</a> of the world's largest fisheries — an <a href="https://www.floridamuseum.ufl.edu/science/seagrass-meadows-harbor-wildlife-for-centuries/" target="_blank" rel="noopener noreferrer">estimated 70%</a> of fish habitats in Florida alone.</p><p>Conversely, their disappearance can contribute to die-offs of marine life. The loss of more than 20 square miles of seagrass in Florida's Biscayne Bay may have helped set the stage for a widespread <a href="https://www.wlrn.org/2020-08-14/the-seagrass-died-that-may-have-triggered-a-widespread-fish-kill-in-biscayne-bay" target="_blank">fish kill</a> in summer 2020. Lack of grasses to produce oxygen left the basin more vulnerable when temperatures rose and oxygen levels dropped as a result, says Florida International University professor Piero Gardinali.</p>
Damaged Systems, a Changing Climate<p>Governments and conservationists around the world have already put a lot of effort into coastal restoration efforts. And that's helped some seagrass populations.</p><p>Where stressors remain, though, restoration grows more complicated. <a href="https://www.rug.nl/research/portal/en/publications/the-future-of-seagrass-ecosystem-services-in-a-changing-world(3a8c56db-7bed-4c9e-ac7f-c72453e2a102).html" target="_blank">Research</a> published this September found that only 37% of seagrass restorations have survived. Newly restored meadows remain vulnerable to the original stressors that depleted them, as well as to storms — and <a href="https://www.ecowatch.com/tag/climate-crisis">climate change</a>.</p>
Seagrass in Dry Tortugas National Park, Florida. Alicia Wellman / Florida Fish and Wildlife / CC BY-NC-ND 2.0<p>In Chesapeake Bay a cold-water species of seagrass is currently hitting its heat limit, especially in summer, according to Alexander Challen Hyman of University of Florida's School of Natural Resources and Environment. As waters continue to warm due to climate change, the species likely will disappear there.</p><p>Climate-driven sea-level rise complicates the problem as well. Seagrasses thrive at specific depths — too shallow and they dry out or are eaten, too deep and there isn't enough light for photosynthesis.</p>
But There’s Good News, Too<p>Luckily, left to its own devices, a seagrass meadow can flourish for hundreds of years, according to a <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2019.1861" target="_blank" rel="noopener noreferrer">paper</a> published last year by Hyman and other researchers from the University of Florida. The researchers arrived at their conclusion by looking at shells of living mollusks and fossil shells to estimate the ages of meadows in Florida's Big Bend region on the Gulf Coast.</p><p>That area has extensive, relatively pristine seagrass meadows. "Our motivation was to understand the past history of these systems, and shells store a lot of history," said co-author Michal Kowalewski.</p><p>A high degree of similarity between living and dead shells indicates a stable area, while a mismatch suggests an area shifted from seagrass to barren sand. The researchers found that long-term accumulations of shells resembled living ones, suggesting that the seagrass habitats have been stable over time.</p><p>That stability allows biodiversity to thrive, creating conditions where specialist species can survive and flourish, according to Hyman.</p><p>Discovering the long-term stability of seagrass meadows has implications for choosing restoration sites, Kowalewski notes.</p><p>"There must be reasons they thrive in one place, while a mile away they don't and fossil data says they probably never did," he said. "If we remove a seagrass patch, we cannot hope to plant it somewhere else. It's not just the seagrass that is special. The location at which it's found is special, too."</p><p>A better approach is conserving these habitats in the first place, but we're not doing enough of that right now. The UN reports that marine protected areas safeguard just 26% of recorded seagrass meadows, compared with 40% of coral reefs and 43% of mangroves.</p>
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