Friday marks the final day of the United Nations COP19 climate change conference in Warsaw, Poland. It also marks two weeks since a massive typhoon swept across the Philippines, leaving more than 5,000 people dead and many more injured, ill, homeless and hungry.
Much has been said of the possible connections between climate change and Super Typhoon Haiyan -- at least to the extent that similarly fierce storms are expected to strike more often and more intensely in the decades ahead. But one issue intersecting both global warming and extreme weather has received little attention: how changes to the natural landscape may be putting public health at greater risk.
"If we followed good landscape policies, we would definitely have fared better against the typhoon," Tony La Vina, climate negotiator for the Philippines, told The Huffington Post in an email from Warsaw.
Human alterations of the land -- from deforestation to erosion caused by modern agriculture -- can speed climate change by releasing stores of carbon. They can also prevent the landscape from providing incidental benefits to humans, such as filtering water, thwarting the spread of infectious disease and buffering against storm surges, flooding and landslides. Experts also warn that a changing climate may be making the consequences of these losses all the worse.
"Natural defenses are important against extreme weather events, whether they are a result of sustainable forest management or plain good land use decisions," added La Vina, who is also dean of the School of Government at Ateneo de Manila University.
A report published this week details what lead author Dr. Samuel Myers of the Harvard School of Public Health calls the "quiet public health crisis" of landscape change.
Roughly half of the world's temperate and tropical forests have been cut down, write members of the Health and Ecosystems: Analysis of Linkages (HEAL) consortium in the peer-reviewed journal Proceedings of the National Academy of Sciences. Meanwhile, half of all ice-free, desert-free land has been converted to crop lands or pasture, and more than 800,000 dams currently impede the flow through more than 60 percent of the world's rivers.
The report details a wide range of potential health impacts, including the loss of sources for pharmaceutical drugs and critical nutrients, as well as diminished protection from natural hazards and diseases, such as cholera, in a storm's wake.
"As you impoverish natural systems -- cut trees, remove species -- you reduce the resilience of those systems to respond to these kinds of perturbations," said Myers, also of Harvard Medical School.
The effects of such perturbations can linger. Many Filipinos are now scrambling for clean water, shelter and food, especially those who have relied on natural systems for these necessities. The most vulnerable, explained Myers, are often those who can't afford the engineered infrastructure and markets that have replaced those same natural benefits. Such people are likely the ones without brick-and-mortar homes, for example, or access to adequate sewage systems.
Further, damage to the Philippines' health infrastructure -- both physical and social -- exacerbates the problem by eliminating mechanisms used to keep endemic diseases in check.
The effects of these losses aren't confined to poor populations, or even to any one storm-ravaged nation.
More than 60 percent of emerging infectious diseases in the last six decades, including ebola, SARS and HIV-AIDS, have originated in animals. Nearly half of those have been linked to changes in land use. Experts predict the next big pandemic will likely start in a wild animal such as a bat or primate. They're keeping their eyes are on southeast Asia and other tropical nations as likely sites for any such disease's jump to humans.
The Philippines is one such hot spot, noted Peter Daszak, president of EcoHealth Alliance, a New York-based organization of scientists dedicated to the dual goals of conservation and public health.
He added that Typhoon Haiyan may further escalate the risk of biological spill-over.
"With events like this typhoon, you've got people migrating and moving into new areas. You've got people whose food supply is gone, so they start looking around for wildlife," said Daszak. "You've got mixing of groups in refugee camps, and you've got a lot of stress and behavior changes as people try to deal with this."
Research by Daszak and others has found that all of the above are among potential predictors of the start of a pandemic. Meanwhile, climate and land use changes, each on their own, have been linked to the emergence and spread of infectious diseases.
To get at the root of these problems, rather than just reacting to an outbreak, Daszak and Myers suggested that scientists need to do a better job of putting a price tag on the services provided by natural landscapes, including biodiversity's ability to buffer outbreaks.
The most popular landscape-preserving economic strategy is currently the United Nations collaborative initiative on Reducing Emissions from Deforestation and forest Degradation. Its daughter program, REDD+, extends the original carbon-trading scheme to consider some ecosystem services.
Delegates in Warsaw agreed Friday on how developing nations can qualify for these programs, with efforts to reduce carbon emissions through forest preservation and the like. Earlier this week, Britain, Norway and the U.S. together allocated $280 million towards the fund.
Still, the schemes don't take into account the health benefits provided by a robust ecosystem.
"If we can link that in, then suddenly that patch of forest becomes much more valuable," said Daszak.
EcoHealth Alliance was awarded a grant from the U.S. Agency for International Development in September to study disease emergence and climate change in Asia, and to try to put a dollar figure on some of those benefits.
"We have an intuitive feel for ecosystem services, but we need to turn that into dollar signs to make a difference in policy and help us talk to different stakeholders about land use," said Kris Murray, a research scientist at EcoHealth Alliance.
"If we start mucking around in environments without understanding the full consequences, we can incur costs to the human population," he added. "Intact ecosystems are the common denominator for preventing an outpouring of carbon and potentially preventing new diseases from spilling over."
Of course, human alterations to the landscape aren't always bad for public health -- at least in the short term. Harvard's Myers and his HEAL colleagues point to successful early efforts to reduce malaria in the Tennessee Valley and sub-Saharan Africa by draining swamps that were habitats for mosquitoes. And there are almost always trade-offs: A dam project today might provide clean energy or increased agricultural productivity while also raising the risk of malaria and schistosomiasis for certain groups of people.
It's a complicated puzzle. La Vina, the Philippines climate negotiator, added yet another twist, highlighting how storms such as Typhoon Haiyan can themselves alter landscapes.
"Loss of forests, prime agriculture land, mangroves, fisheries, have not been accounted for," he said. "This is important to measure, as they are directly related to human well-being."