Antarctica loses three trillion tonnes of ice in 25 years
by Jonathan Amos, Victoria Gill
BBC Science correspondents
Antarctica is shedding ice at an accelerating rate. Satellites monitoring the state of the White Continent indicate some 200 billion tonnes a year are now being lost to the ocean as a result of melting.
This is pushing up global sea levels by 0.6mm annually - a three-fold increase since 2012 when the last such assessment was undertaken.
Scientists report the new numbers in the journal Nature.
The researchers say the losses are occurring predominantly in the West of the continent, where warm waters are getting under and melting the fronts of glaciers that terminate in the ocean.
"We can''t say when it started - we didn''t collect measurements in the sea back then," explained Prof Andrew Shepherd, who leads the Ice sheet Mass Balance Inter-comparison Exercise (Imbie).
"But what we can say is that it''s too warm for Antarctica today. It''s about half a degree Celsius warmer than the continent can withstand and it''s melting about five metres of ice from its base each year, and that''s what''s triggering the sea-level contribution that we''re seeing," he told BBC News.
Antarctica''s ice melt ''has accelerated''
Space agencies have been flying satellites over Antarctica since the early 1990s. Europe, in particular, has an unbroken observation record going back to 1992.
These spacecraft can tell how much ice is present by measuring changes in the height of the ice sheet and the speed at which it moves towards the sea. Specific missions also have the ability to weigh the ice sheet by sensing changes in the pull of gravity as they pass overhead.
Imbie''s job has been to condense all this information into a single narrative that best describes what is happening on the White Continent.
Glaciologists usually talk of three distinct regions because they behave slightly differently from each other. In West Antarctica, which is dominated by those marine-terminating glaciers, the assessed losses have climbed from 53 billion to 159 billion tonnes per year over the full period from 1992 to 2017.
On the Antarctic Peninsula, the finger of land that points up to South America, the losses have risen from seven billion to 33 billion tonnes annually. This is largely, say scientists, because the floating ice platforms sitting in front of some glaciers have collapsed, allowing the ice behind to flow faster.
Globally, sea levels are rising by about 3mm a year. This figure is driven by several factors, including the expansion of the oceans as they warm. But what is clear from the latest Imbie assessment is that Antarctica is becoming a significant player.
"A three-fold increase now puts Antarctica in the frame as one of the largest contributors to sea-level rise," said Prof Shepherd, who is affiliated to Leeds University, UK.
"The last time we looked at the polar ice sheets, Greenland was the dominant contributor. That''s no longer the case."
In total, Antarctica has shed some 2.7 trillion tonnes of ice since 1992, corresponding to an increase in global sea level of more than 7.5mm.
"At the moment, we have projections going through to 2100, which is sort of on a lifetime of what we can envisage, and actually the sea-level rise we will see is 50/60cm," said Dr Whitehouse.
"And that is not only going to impact people who live close to the coast, but actually when we have storms - the repeat time of major storms and flooding events is going to be exacerbated," she told BBC News.
One-third of the world’s nature reserves are under threat from humans
by The Conversation, agencies
In the 146 years since Yellowstone National Park in the northwestern United States became the world’s first protected area, nations around the world have created more than 200,000 terrestrial nature reserves. Together they cover more than 20 million km˛, or almost 15% of the planet’s land surface – an area bigger than South America.
Governments establish protected areas so that plants and animals can live without human pressures that might otherwise drive them towards extinction. These are special places, gifts to future generations and all non-human life on the planet.
But in a recent study published in Science, we show that roughly one-third of the global protected area estate (a staggering 6 million km˛) is under intense human pressure. Roads, mines, industrial logging, farms, townships and cities all threaten these supposedly protected places.
It is well established that these types of human activities are causing the decline and extinction of species throughout the world. But our new research shows how widespread these activities are within areas that are designated to protect nature.
We assessed the extent and intensity of human pressure inside the global protected area estate. Our measure of human pressure was based on the “human footprint” – a measure that combines data on built environments, intensive agriculture, pasturelands, human population density, night-time lights, roads, railways, and navigable waterways.
Astoundingly, almost three-quarters of countries have at least 50% of their protected land under intense human pressure – that is, modified by mining, roads, townships, logging or agriculture. The problem is most acute in western Europe and southern Asia. Only 42% of protected land was found to be free of measurable human pressure.
Across Earth, there is example after example of large-scale human infrastructure within the boundaries of protected areas. Major projects include railways through Tsavo East and Tsavo West national parks in Kenya, which are home to the critically endangered eastern black rhinoceros and lions famous for their strange lack of manes. Plans to add a six-lane highway alongside the railway are well underway.
Many protected areas across the Americas, including Sierra Nevada De Santa Marta in Colombia and Parque Estadual Rio Negro Setor Sul in Brazil, are straining under the pressure of densely populated nearby towns and rampant tourism. In the US, both Yosemite and Yellowstone are also suffering from the increasingly sophisticated tourism infrastructure being built inside their borders.
In highly developed, megadiverse countries such as Australia, the story is bleak. A classic example is Barrow Island National Park in Western Australia, which is home to endangered mammals such as the spectacled hare-wallaby, burrowing bettong, golden bandicoot and black-flanked rock-wallaby, but which also houses major oil and gas projects.
While government-sanctioned, internationally funded developments like those in Tsavo and Barrow Island are all too common, protected areas also face impacts from illegal activities. Bukit Barisan Selatan National Park in Sumatra - a UNESCO world heritage site that is home to the critically endangered Sumatran tiger, orangutan and rhinoceros - is also now home to more than 100,000 people who have illegally settled and converted around 15% of the park area for coffee plantations.
Protected areas underpin much of our efforts to conserve nature. Currently, 111 nations have reached the global standard 17% target for protected land outlined in the United Nations’ Strategic Plan for Biodiversity. But if we discount the supposedly protected land that is actually under intense human pressure, 74 of these 111 nations would fall short of the target. Moreover, the protection of some specific habitat types – such as mangroves and temperate forests – would decrease by 70% after discounting these highly pressured areas.
Governments around the world claim that their protected areas are set aside for nature, while at the same time approving huge developments inside their boundaries or failing to prevent illegal damage. This is likely a major reason why biodiversity continues to decline despite massive recent increases in the amount of protected land.
Our results do not tell a happy story. But they do provide a timely chance to be honest about the true condition of the world’s protected areas. If we cannot relieve the pressure on these places, the fate of nature will become increasingly reliant on a mix of nondescript, largely untested conservation strategies that are subject to political whims and difficult to implement on large enough scales. We can’t afford to let them fail.
But we know that protected areas can work. When well-funded, well-managed and well-placed, they are extremely effective in halting the threats that cause species to die out. It is time for the global conservation community to stand up and hold governments to account so they take conservation seriously. This means conducting a full, frank and honest assessment of the true condition of our protected areas.
Globally, the real-life footprint of habitat loss is spreading, by Michelle Chen.
Globally, the real-life footprint of habitat loss is spreading; more than half the areas designated over the past quarter century have seen increased human pressure. Overall, researchers warn we may be vastly underestimating both the ecological damage that’s already taken place, and the threats looming on the horizon.
The “protected” designation covers everything from rain forests to grasslands to icy tundras. As a political instrument, the protected designation serves as the last line of defense in the effort to conserve nature and maintain biodiversity in an era when human societies are intermeshing with nearly every terrain around the planet.
Though the study doesn’t go so far as to suggest the label of “protected” is useless, it’s a call to environmental authorities to incorporate more extensive data mapping into their environmental monitoring to gain a more realistic picture of the nature and scale of surrounding environmental threats.
Though the United States has historically been a leader in wildlife conservation efforts, the Trump administration and EPA chief Scott Pruitt have steamrolled Clean Air and Clean Water Act regulations, while championing policies to spur the commercialization of public lands.
The administration has directly attacked wilderness areas by working to strip protections from national monuments, such as the Bears Ears and Grand Escalante sites in Utah—which cover several million acres of iconic Western landscapes—while conservative lawmakers last year moved to promote oil drilling on the coastal plain of the pristine Arctic National Wildlife Refuge.
Trump is mirroring the assault on protected areas now trending across the globe: a steady creep of commercialization and deregulation, promoted by governments that seek to exploit and privatize whatever land has not yet been consumed.
The gap between formal maps and the actual landscape suggests that current laws and regulations are wildly out of sync with what’s happening on the ground. This is in part because of arbitrary, widely varying legal definitions of protection across national and regional borders. Moreover, the study’s analysis does not include longer term trends influencing the terrain, including human-induced climate change or conflict, which might have even more extreme long-term environmental impacts.
Yet, in every area impacted by humans, local air and water quality could be undermined by the sprawl of industry and transportation and the overarching pressures of continuous population growth. The impact of a single road’s cutting into a forested area could have a profound impact on soil and pollution levels. Even settling a small town could eliminate crucial range lands that grazing species rely on.
Razing forests for farmland could displace critical species and stifle local biodiversity. When food chains are disrupted, animal and plant life could be devastated, and the consequences eventually reverberate in human communities, destabilizing societies and economies locally and then globally.
According to researcher and co-author of the study Kendall Raward Jones of University of Queensland, “The impacts we are finding are in many cases not sustainable—we’re talking about cities, massive road and railway projects, industrial agriculture, etc.” Often these are government-supported infrastructure projects aimed at boosting economic development, and their conflict with regional ecosystems attests to the challenges of sustainable development in areas where populations keep demanding more space, resources, and transit networks.
It may be too late to turn back the clock on human development, but researchers hope the new data help governments chart a course toward a more sustainable regulatory regime. The more accurate data authorities have on the real human impact in protected lands, the better equipped society is to restructure environmental protections to place appropriate limitations on industrial and social activity in conservation areas dynamically, not just on a piece of paper.
According to Jones, regulators need to take a more three-dimensional approach to assessing the level of human activity on an area designated for official conservation: “I don’t think that human encroachment is inevitable. We know that protected areas, when well-funded and well-managed, can be very effective at stopping human activities which threaten biodiversity. The problem is that by focusing mainly on the size of the area under ‘protection,’ global conservation targets allow nations to get away with designating land as ‘protected’ while not actually following through with the regulations and enforcement needed to make these areas effective.”
We manage what we measure: Real conservation is possible only if policy-makers, scientists, and the public share an understanding of collective responsibility and how to balance human needs and ecological imperatives. It may seem virtuous for governments to label a piece of nature for “protection,” but it means nothing when the stroke of an executive pen can just as easily erase it into oblivion.
* Michelle Chen is a contributing writer for The Nation, and co-producer of the “Asia Pacific Forum” on Pacifica Radio in New York.
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