by DK
UNESCO
UNESCO, an agency of the UN based in Paris, France, was founded in 1946 to promote international collaboration for peace and security. It was established in line with the United Nations Charter, through education, science, and culture. Today, the organization has 195 member states.
UNESCO continues the work begun by the League of Nations International Committee on Intellectual Cooperation in the 1920s, which was interrupted by the outbreak of World War II. Today, members aim to achieve their objectives by sponsoring international educational and scientific programs. These include dedicated projects that promote and protect human rights and sustainable development, while encouraging cultural diversity.
The organization is perhaps best known for establishing internationally recognized World Heritage Sites, which aim to preserve as many aspects as possible of the world’s diverse cultural and natural heritage.
See also: Human activity and biodiversity • The ecosystem • The peaceful coexistence of man and nature • Renewable energy • Environmental ethics • Sustainable Biosphere Initiative
IN CONTEXT
KEY FIGURE
Mark L. Shaffer (1949–)
BEFORE
1964 The IUCN publishes its first Red List of threatened mammal and bird species.
1965 In The Destruction of California, ecologist Raymond Dasmann charts the rapid loss of flora and fauna in the state.
1967 The Theory of Island Biogeography by Robert MacArthur and Edward O. Wilson explores island patterns of immigration and extinction.
AFTER
2003 Population viability analysis (PVA) of the Fender’s blue butterfly is used to guide conservation in the US.
2014 PVA studies in the Sonoran Desert, US, help assess the response of birds and reptiles to climate change.
Population viability analysis (PVA), or extinction risk assessment, is a process used to estimate the probability that a population of a target species has the ability to sustain itself for a specific time, be it 10, 30, or 100 years. A key feature of PVA is the definition of minimum viable population sizes and minimum habitat areas—information which can then inform decisions on conservation priorities.
A tool for conservationists
PVA combines both statistics and ecology to calculate the fewest organisms required for a species to survive long-term in its preferred habitat. This minimum number also dictates the amount of suitable habitat that the species needs. PVA is a useful tool for conservationists when lobbying governments and developers to give protected status to an area. Armed with a PVA, they can explain precisely why reducing a stretch of forest, heathland, or reedbed will threaten certain flora or fauna. Protecting an area that is extensive enough to support a large species also benefits many smaller organisms sharing the same environment.
A number of creatures can only survive in environments where human disturbance is minimal. This is especially true for those that live in specialist habitats, such as certain owls in old-growth forest, reptiles on acid heathland, or amphibians in fast-flowing, unpolluted streams. However, as the human population grows, there is a constant demand for land for building, agriculture, leisure, roads, or forestry. This pressure is a particular threat to species that cannot easily adapt and move elsewhere. Where they are already confined to “islands” of suitable habitat, it takes no more than a low level of environmental damage or human disturbance to nudge them toward extinction.
Fender’s blue butterfly was not seen after the 1930s and was deemed extinct until it was rediscovered in 1989. It is endangered, but small populations live in northwest Oregon.
Counting grizzlies
In 1975, grizzly bear numbers were shrinking in Yellowstone National Park. Only an estimated 136 of the bears were left, and this isolated population was considered to be endangered. As part of his doctoral research, Mark L. Shaffer began to study the long-term sustainability of this geographically isolated grizzly bear population.
Shaffer, a pioneer of population viability analysis, applied four factors that he considered would decide their fate. The first was demographic stochasticity: irregular, unpredictable fluctuations in numbers, age, gender, and birth and death rates. For example, if the overwhelming majority of animals in a population are males, breeding success will be poorer than in a more evenly balanced population, and will influence its chances of survival. The second consideration was environmental stochasticity: unpredictable fluctuations in environmental conditions, such as habitat and climate changes, which may affect the availability of food and shelter. The third was natural catastrophes, such as forest fires or floods. The fourth of Shaffer’s factors was genetic changes, including problems created by inbreeding. For each of these, statistical modeling can determine a range of possibilities.
Since Shaffer’s initial research in the 1970s and ’80s, and subsequent new management and conservation strategies, grizzlies have extended their habitat by more than 50 percent within the extensive Greater Yellowstone Ecosystem—an area of 34,375 sq miles (89,031 sq km) that has the national park at its core. In 2014, the US Geological Survey estimated that around 757 bears lived in the ecosystem, based on 119 sightings of grizzly sows and cubs. However, the population had dropped to around 718 in 2018, and population modllers have suggested that Yellowstone may have reached its maximum carrying capacity—the largest number of animals an area of suitable habitat can support. In 2017, grizzlies were briefly removed from the threatened species list, but their protections were restored by a federal judge in 2018.
“Uncertainty is just about the only certainty in PVA.”
Steven Beissinger
American conservation biologist
Vulnerability of small populations
A minimum viable population has to be of a sufficient size not only to maintain itself under average conditions but also to endure extreme events. Mark Shaffer likened this to a reservoir built to withstand the type of flood that occurs only once in 50 years, but not a devastating once-in-a-century flood.
Small populations are especially vulnerable to multiple threats occurring successively. The Heath Hen in New England, US, had been widespread in colonial times, but relentless hunting for food and sport caused a dramatic decline in Heath Hen numbers by 1908. In that year, the last surviving population on the island of Martha’s Vineyard was given protected status. However, a catastrophic wildfire during the 1916 breeding season, severe winters, inbreeding, disease, and heavy predation by birds of prey all combined to push the Heath Hen population below a viable level. By 1927, only two females remained, and the species was extinct by 1932.
How studies are devised
PVA studies are now conducted in several ways. The simplest type is the time-series PVA, which looks at the entirety of a population over a period of time in order to calculate a rough average growth trend and any variations. In such studies, all individuals are treated as identical.
Demographic PVAs tend to be more precise and detailed. They are based on estimated reproductive and survival rates for different age bands within the population. Such analyses require much more data, but can provide extra information on the needs and vulnerability of different sections of the population, fueling a case for conservation where protection is required. As reliable information on age ranges and breeding rates is often not available for small, threatened populations, ecologists sometimes use data from other populations of the same species—or a different but similar species—to conduct a PVA. However, the results are variable, even in populations of the same species in the same area. In a 2015 study of three colonies of California sea lion in the Gulf of California, “surrogate” data from one colony was used to make forecasts on the other two; they proved valid for one colony, but not the other.
A female grizzly and her cubs forage in Yellowstone. A female’s home range is 300–550 sq miles (775–1,400 sq km), while a male’s is as much as 2,000 sq miles (5,000 sq km).
“Technology is increasingly allowing scientists and policym
akers to more closely monitor the planet’s biodiversity and threats to it.”
Stuart L. Pimm
American–British biologist
Making a difference
Methods are still being refined, but PVA has now become a cornerstone of conservation biology. PVAs have been applied to populations as varied as island foxes in California, sea otters in Alaska, Fender’s blue butterflies and Northern Spotted Owls in Oregon, and bottlenose dolphins off the coasts of Argentina and Australia. With the development of increasingly efficient computer programs incorporating ever more variables, PVA will undoubtedly be used even more effectively in the future. It is impossible to predict every extinction, but PVA provides tools for identifying endangered populations and determining the management actions likely to be most effective in improving population viability, and preserving a species at risk.
“Population viability analysis can indicate how urgently recovery efforts need to be initiated in specific populations.”
William F. Morris
American biologist
The island foxes of the Channel Islands, off California, numbered fewer than 200 in the late 1990s. By 2015, there were more than 5,000, but on one island, a subpopulation is still at risk.
A Japanese study
The Japanese Rock Ptarmigan lives in the Japanese Alps at an altitude of around 8,200 ft (2,500 m). Its population of some 2,000 birds is divided into several small communities on mountain peaks. When a combination of climate warming and predators moving further up the mountains prompted fears for its survival, ecologist Ayaka Suzuki and his team set out to find the minimum viable population size for the birds on Mount Norikura. The team collected population growth data, including the number of female offspring that survived to the next breeding season and the annual survival rate of all birds. Their calculations included variables for a range of offspring from each pair.
Their findings indicated that there was a relatively low risk of extinction in the next 30 years, even if the starting population was only 15. One potential conclusion is that the Mount Norikura population is strong enough to supplement declining populations on other mountains.
See also: Ecological resilience • Climax community • Metapopulations • Mass extinctions • Deforestation
IN CONTEXT
KEY FIGURES
Bert Bolin (1925–2007), Intergovernmental Panel on Climate Change (1988–)
BEFORE
1955 American scientist Gilbert Plass concludes that higher concentrations of carbon dioxide (CO2) will lead to higher temperatures.
1957 American scientist Roger Revelle and Austrian physical chemist Hans Suess jointly publish a report proving that the oceans will not absorb the excess CO2 in the atmosphere.
1968 British glaciologist John H. Mercer theorizes a catastrophic rise in sea levels in the next 40 years due to the collapse of Antarctic ice sheets.
AFTER
2020 Plans created by the Paris Agreement to combat climate change are due to be implemented.
Since the Industrial Revolution, humans have been altering Earth’s natural environment through increased carbon dioxide (CO2) emissions. Societies have become more technologically advanced, but this technology—from coal-powered trains, ships, and factories, to oil-fueled cars and planes—has had an adverse impact on the natural world and the species inhabiting it. As scientists have become more aware of the human causes of climate change, global research groups have been formed to study the phenomenon and suggest ways in which humanity can halt, if not reverse, the damage.
The effects of climate change are varied. As more CO2 in the atmosphere creates global warming, this causes the polar ice caps to melt, the oceans to warm and rise, and species that are unsuited to warmer oceans to die out. Global weather patterns are also changing: hurricanes in the North Atlantic region have increased in intensity, leaving devastation and death in their wake. Fires and droughts have become more frequent in dry areas; winters are more severe in colder climates. Areas of the world already susceptible to extreme weather-related catastrophes, such as those impacted by tropical monsoons, are seeing the most severe repercussions, especially in terms of loss of life and habitat.
Firefighters battle flames from the “Holy Fire” that ravaged Orange County, California, in 2018. Higher temperatures led to an extended and difficult forest fire season.
Global cooperation
Scientists have been aware that human actions contribute to climate change since 1896, when Swedish scientist Svante Arrhenius suggested that people burning fossil fuels were adding to global warming. It was not until the 1970s, however, that governments began to act upon this knowledge. Around this time, the general public had begun to be made aware of the reality of climate change due to news articles and broadcasts that shared the bleak outlooks of climate scientists with the wider world.
International efforts to halt or delay climate change began with the first United Nations conference on the environment, which was held in Stockholm, Sweden, in 1972. The conference paid little attention to the issue of climate change compared to other environmental issues—such as pollution and renewable energy—but did create the United Nations Environment Programme (UNEP), an agency to oversee environmental policies and programs such as ecosystem management, natural disaster relief, and antipollution activities. UNEP later became responsible for coordinating UN efforts against climate change.
In 1987, UN members also agreed to the Montreal Protocol, pledging to protect Earth’s ozone layer by ending the use of ozone-depleting substances. Although it was not specifically designed to combat climate change, the agreement, which was ratified by all UN member states, did reduce greenhouse gas emissions.
Creation of the IPCC
In 1988, the Intergovernmental Panel on Climate Change (IPCC) was established in Geneva, Switzerland, by two United Nations organizations: UNEP, and the World Meteorological Organization (WMO). Swedish meteorologist Bert Bolin—who served on the Advisory Group on Greenhouse Gases that the IPCC supplanted—was the panel’s first chairman.
The IPCC was created to serve as a globally coordinated response to climate change linked to human activity. It issues reports based on scientific research in support of the main international treaty on climate change: the UN Framework Convention on Climate Change (UNFCCC), which was signed at the Earth Summit in Rio de Janeiro, Brazil, in 1992. The IPCC’s work also involves issuing the Summary for Policymakers (SPM), which provides summaries of climate change research to governments around the world to help them understand the threats to humans and the environment as a result of climate change.
An Inconvenient Truth, a 2006 documentary on climate change by former US Vice President Al Gore, aimed to educate the public on the causes and effects of climate change.
“… human beings are now carrying out a large-scale geophysical experiment of a kind that could not have happened in the past…”
Roger Revelle and Hans Suess
The Kyoto plan
Nine years after the creation of the IPCC, in 1997, UN members signed the Kyoto Protocol, which sought to improve regulation of global carbon emissions. This protocol was the first agreement among nations to mandate country-by-country reductions in greenhouse gas emissions, aiming to reduce them to levels that would stop humans from negatively impacting the world’s ecosystems.
Although signed in 1997, the Kyoto Protocol did not take effect until 2005. At the end of the first commitment period in 2012, all signatory nations had achieved their target reduction except for Canada, which withdrew from the protocol because it could not meet its targets. Australia also failed to reduce emissions, but in the initial period, their target was set as an 8 percent increase. Most nations are on track to meet their target for 2020, except for Norway, which had set a very high target (a 30–40 percent reduction from 1990 levels).
An underwater cabinet meeting is held in the Maldives in 2009 to call for action against climate change. Rising sea levels could mean that the
nation is eventually swallowed by the ocean.
Paris and the future
The Kyoto Protocols set targets for nations to meet from 2005 to 2020. After 2020, signatory nations will begin to abide by a new protocol: the Paris Agreement. In November 2016, after decades of calls for a more aggressive global resolution climate change, the Agreement was signed by 195 UNFCCC member countries at the UN headquarters in New York City. Like Kyoto, the primary aim of the Paris Agreement is to cut greenhouse gas emissions to agreed-upon levels.
With the decision of Syria to sign the Paris Agreement in 2017, the United States became the only country in the world not to take part in the agreement. Although the US initially signed the agreement under Barack Obama’s presidency, his successor, Donald Trump, has rejected the agreement, claiming that it asked too much of the United States and too little of other nations. This decision struck a blow to the other signatories; as well as having plenty of wealth to fund climate research, the US is also the world’s second-largest greenhouse gas emitter. President Trump has since clarified his position by saying that he believes climate change to be a natural phenomenon from which the world can “come back” without significant changes to human behavior.
