Environment

Bottled water—a general term referring to natural mineral water, spring water, and purified water supplied to consumers in bottles—is the world’s fastest-growing commercial beverage. Global consumption of bottled water more than doubled between 1997 and 2005, reaching a total of 164.5 billion liters, or 25.5 liters per person.1 (See Table 1.) While Europe and North America still dominate the bottled water market, consumption in Asia and South America has increased dramatically over the past five years, expanding at 14 percent and 8 percent a year respectively.2

The United States is the world’s largest consumer of bottled water, with Americans drinking 28.7 billion liters in 2005.3 But consumption per person is a different story: in 2005 each Italian, on average, drank more bottled water than anyone else in the world—192 liters, compared with 99 liters for Americans.4 Among the top 10 countries, Brazil, China, and India have doubled or even tripled consumption between 2000 and 2005, though per capita intake in China and India is still far below the global average.5 Altogether, almost three quarters of the world’s bottled water is consumed in the top 10 countries.6

Worldwide, people buy bottled water in order to have safe drinking water, especially consumers in developing countries who face unreliable municipal water supplies, water scarcity, and continual water contamination.7 In most industrial countries, however, where municipal water is better regulated, people drink bottled water also for better taste, for convenience, and as a substitute for other beverages.8 In the United States, calorie-free bottled water has attracted consumers concerned about obesity.9

Urbanization, improved living standards, office working environments, and aggressive marketing strategies have helped boost the global sales of bottled water.10 Home and office delivery of bottled water has become a popular service and supplies nearly 28 percent of the water consumed.11

The difference in cost between bottled and tap water is staggering: the bottled version costs from 240 times to more than 10,000 times as much.12 The Pacific Institute, a California-based think tank, found that bottled water sold in most industrial countries costs $500–1,000 per cubic meter, compared with 50¢ per cubic meter of California’s high-quality tap water.13 Most of what consumers pay goes into production, packaging, transportation, advertising, retailing, marketing, and profits—not the water itself. In 2005, selling bottled water in the United States generated more than $10 billion in revenue.14

Social injustice remains a big concern in terms of bottled water consumption. People who desperately need a better supply of drinking water are usually not able to afford the bottled version.15 In India, upper-class to lower-middleclass families are the main consumers, while tourists dominate bottled water consumption in rural areas.16 The U.N. Development Programme’s Human Development Report 2006 notes that bottled water consumption generates nontangible health benefits but expands the gap between industrial and developing countries.17

Bottled water is regulated as a food product in the United States and Canada, while the European Union has two directives: one on natural mineral water and another on drinking water that includes bottled spring or purified water.18 Regulation codes for bottled water generally cover the composition, contaminants, processing requirements, and labeling.19 The Codex Alimentarius—an international food code initiated by the World Health Organization and the Food and Agriculture Organization— can be adopted by countries that lack national regulations.20

Based on a four-year study of the bottled water industry in the United States, including a test of more than 1,000 bottles of 103 brands of water, the Natural Resources Defense Council reported in 1999 that bottled water is not always safe to drink or better than tap water.21 Regulations concerning bottled water are generally the same as tap water but weaker in certain standards for microbial contaminants. The U.S. Food and Drug Administration (FDA), which regulates bottled water at the federal level, permits this product to contain certain levels of fecal coliforms, while the Environmental Protection Administration does not allow fecal coliforms in city tap water.22 And when violating the weaker FDA standards, bottled water may still be sold if it is labeled “containing excessive chemical substances” or “excessive bacteria.”23 Bottled water violations are not always reported to the public, or the products are recalled up to 15 months after the problematic water was produced, distributed, and sold.24

The environmental impacts of bottled water also need to be considered. Excessive withdrawal of natural mineral water or spring water to produce bottled water has threatened local streams and groundwater aquifers.25 And producing, bottling, packaging, storing, and shipping bottled water uses significant amounts of energy.26 In addition, millions of tons of oil-derived plastics— mostly polyethylene terephthalate (PET)— are used to make the water bottles.27

PET bottles have comparatively lower environmental impacts than glass or aluminum by requiring less energy to recycle or remanufacture, and they do not release chlorine into the atmosphere when incinerated, which PVC does.28 But without proper recycling, massive amounts of PET bottles in the waste stream pose serious challenges to land uses as well as to water and air quality around landfills.29

In the United States, about 2 million tons of PET bottles end up in landfills each year.30 According to the National Association for PET Container Resources, U.S. use of PET for bottled water without carbonization grew more than 20 percent in 2005, while usage for carbonated soft drinks dropped.31 The recycling rate of PET rose slightly to 23.1 percent in the United States that same year, with a total of 2.3 million tons of waste generated. But this was still far below the 39.7-percent recycling rate achieved 10 years earlier.32 Sales of plastic water bottles under 1 gallon have skyrocketed over the past decade in the United States, from 2.7 billion in 1997 to 28.6 billion in 2005.33 Most of the water is consumed far from residence-based recycling programs. Adding a refund value—a nickel or dime—to the price of bottled water might give consumers an incentive to recycle. The 11 states embracing “bottle bills” with refund provisions have achieved three to four times the recycling rate of other states.34

At the same time that marine scientists are reporting that the world’s growing appetite for seafood may drive major fish populations to extinction in coming decades, humans are undermining marine health by using the oceans as a dumping ground.1 (See Figure 1.) From inland farms and coastal sewage systems to transoceanic cruises and greenhouse gases, 80 percent of pollutants in oceans originate on land.2 And although certain national and international laws have curbed oil spills and dumping by cruise ships, the amount of contaminants accumulating in oceans grows, even as the oceans’ ability to dilute these substances declines.3

Many substances that are carried into the world’s rivers and streams eventually find their way into coastal waterways and oceans. Around 60 percent of the wastewater discharged into the Caspian Sea is untreated, for example, while in Latin America and the Caribbean the figure is close to 80 percent and in large parts of Africa and the Indo-Pacific region the proportion is as high as 90 percent.4 In the United States alone, more than 3.2 trillion liters of sewage—including human waste, detergents, and household chemicals—gush untreated into waterways every year.5 Worldwide, an estimated $56 billion is needed annually to address this enormous wastewater problem.6 By some estimates, the fastest-growing source of ocean pollution is the chemicals, human waste, and trash that run off of coastal city streets into ocean-bound storm drains.7

More than half of the world lives in coastal areas (within 200 kilometers of shore) that cover just 10 percent of Earth’s surface.8 These coastal populations are increasing at twice the rate of inland ones.9 An estimated 70 percent of the world’s tropical coasts have been developed for housing, fish farms, or industrial ports, and the United Nations expects 90 percent will be developed by 2032.10

Nitrogen, phosphorus, and other nutrients from fertilizers, large livestock farms, and septic systems provoke explosive blooms of tiny plants known as phytoplankton, which die and sink to the bottom and then are eaten by bacteria that use up the oxygen in the water.11 This oxygen starvation creates “dead zones” that make it difficult for fish, oysters, sea grass beds, and other marine creatures to survive.12 There are now about 200 of these zones around the world, roughly one third more than just two years ago.13 The most severe cases exceed 20,000 square kilometers, as in the Gulf of Mexico, the Bay of Bengal, the Arabian Sea, the East China Sea, and the Baltic Sea.14

The U.N. Environment Programme (UNEP) estimates that 46,000 pieces of plastic litter— including bits of packaging, cigarette lighters, plastic bags, and diapers—are floating on every square mile of the oceans, a figure that has increased threefold since the 1960s.15 Marine conservation groups estimate that more than a million seabirds and 100,000 mammals and sea turtles die globally each year by getting tangled in or ingesting plastics.16

Even pollution of the atmosphere—in the form of greenhouse gases and resulting climate change—is taking a growing toll on ocean life. Climate change is altering fish migration routes, pushing up sea levels, leading to more coastal erosion, raising ocean acidity levels to a point where they threaten calcium-building species like corals and shellfish, and interfering with ocean currents that move vital nutrients upward from the deep sea.17 The latter generates chaos among plankton, the foundation of the ocean food chain, that ironically help store carbon dioxide in the ocean floor as they die and decompose; the oceans have absorbed about half of the carbon dioxide produced by humans in the last 200 years.18

Humans suffer, of course, when ocean pollution reduces fish populations or stains the pristine nature of beach recreation. Industrial pollutants, like mercury or PCBs, that end up in water bodies are absorbed by fish we eat. In the last half-century, scientists around the world have tracked a 10-fold increase in pollution-fed algae blooms, which have produced toxins that poison sea life, seafood, and even humans swimming in and living near the ocean.19

Some of the most pernicious forms of ocean pollution are generated by the very people and industries that benefit directly from the pristine nature of the seas. Lax state and federal antipollution laws allow the world’s growing fleet of more than 200 cruise ships to dump into the ocean untreated sewage from sinks and showers and inadequately treated sewage from toilets.20 Once ships are three miles from shore, they can dump all untreated sewage, including bacteria, pathogens, detergents, and heavy metals. Each day, a standard cruise ship generates some 114,000 liters of sewage from toilets; 852,000 liters of sewage from sinks, galleys, and showers; seven tons of garbage and solid waste; 57 liters of toxic chemicals; and 26,500 liters of oily bilge water.21

Oceana, an international ocean protection group, launched a campaign to introduce Clean Cruise Ship legislation in California and at the U.S. federal level to prohibit dumping of boat sewage.22 And following an aggressive 11-month grassroots campaign aimed at the world’s second largest cruise line, Royal Caribbean agreed to install advanced wastewater treatment technology on all 29 of its ships.23

Since its formation in 1995, UNEP’s Global Programme of Action for the Protection of the Marine Environment from Land-Based Sources has helped reduce oil discharges and spills into the oceans by 63 percent compared with levels in the mid-1980s.24 And tanker accidents have dropped by 75 percent, partly as a result of the shift to double-hulled tankers.25

The general public, perhaps because people care about eating seafood or because the oceans seem worth protecting, is also beginning to clean up pollution. Beginning in 1986, the Ocean Conservancy organized shoreline cleanups each fall.26 To date, 6.2 million volunteers in International Coastal Cleanups have removed 49 million kilograms of debris from nearly 288,000 kilometers of coasts in 127 nations.27 Nearly 60 percent of all debris is from recreational activities, including fishing lines and nets, beach toys, and food wrappers. An additional 29 percent is cigarette butts and filters.28

In 2005, the Millennium Ecosystem Assessment (MA) determined that “across the range of biodiversity measures, current rates of loss exceed those of the historical past by several orders of magnitude and show no indication of slowing.” 1 Current trends in biodiversity loss show no indication of a slowdown. The MA lists invasive species as one of five direct drivers behind biodiversity loss (the others are land use change, climate change, overexploitation, and pollution).2

Only a small proportion of invasive alien species—living organisms that are moved around the world through human activity and global trade—actually cause harm. But this subset of introduced non-native species, whether brought in intentionally or unintentionally, has major ecological and socioeconomic impacts. And they are found in all major taxonomic groups.3 (See Table 1.)

Invasive species cause a reduction in native biodiversity through predation, parasitism, hybridization, or competition with native species for habitats and resources.4 They alter ecosystem functioning by causing changes in the nutrient and hydrological regime.5 Socioeconomic damages can include loss of livelihoods and the expenditure of vast amounts of resources on control and mitigation of the risks caused by invasives.6

Nearly 30 percent of globally threatened birds are under threat from invasive aliens.7 The problem is more severe on islands: 67 percent of this group of birds on islands are threatened by non-native species.8 The extinction of at least 65 species of birds has been tied to predation by introduced rats, cats, pigs, dogs, and mongooses; to habitat destruction by sheep, goats, and rabbits; and to diseases caused by introduced pathogens.9 For example, predation by rats has caused the near extinction of the Campbell Island teal in New Zealand, while avian malaria has caused the near extinction of birds in Hawaii.10

Candleberry myrtle or firebush, an invader of wet and mesic forests in Hawaii, forms dense, monotypic stands and has a negative effect on the recruitment and persistence of native plant species.11 Firebush, a nitrogen- fixer, has altered primary successional ecosystems in the Hawai’i Volcanoes National Park by quadrupling inputs of nitrogen and is now reported to be spreading through drier submontane forests.12

Five major aquatic weeds that have spread over large areas of the natural and seminatural freshwater ecosystems of South Africa cause water availability and use problems.13 They have reduced the quality of drinking water, increased the incidence of waterborne, waterbased, and water-related diseases, and caused a decline in aquatic biodiversity.14

The global footprint of invasive alien species on biological diversity is yet to be quantified; a measure of the footprint will provide a better understanding of the need and priorities for effective conservation responses.

In 1993, the Office of Technology Assessment of the U.S. Congress documented economic damages of up to $97 billion between 1906 and 1991 due to 79 non-native invasive species.15 More recently, David Pimentel and his colleagues at Cornell University estimated economic damages for the United States, the United Kingdom, Australia, India, South Africa, and Brazil to be in excess of $336 billion per year.16

Practical responses to biological invasions include preventing the intentional and unintentional introduction of invasive aliens, management and control of the ones already present and established, and mitigation of the risks and impacts they cause. The collection and exchange of authoritative data and information is a key component of these responses, and the wide dissemination of summary information helps raise public awareness. Examples of global, regional, national, and thematic information systems include the Global Invasive Species Database (GISD), the North European and Baltic Network on Invasive Alien Species, Pacific Island Ecosystems at Risk, and Non-indigenous Aquatic Species.17 A network that will link all these information systems together, the Global Invasive Species Information Network, is also being developed.18

The most detailed and accurate data on invasive alien species at the global scale is available in the Global Invasive Species Database.19 The GISD is a free searchable source of authoritative information about species that have a negative impact on biodiversity. It aims to facilitate effective prevention and management activities by disseminating specialist knowledge and experience to a broad global audience. Development of the GISD began in 1998 as part of the global initiative on invasive species led by the Global Invasive Species Programme.20

GISD profiles include information on the ecology, impacts, distribution, and range expansion of invasive alien species, along with images and descriptions, information about effective prevention and management options, and contact details for experts on each species. Users include natural resource managers, extension agents, environment and biodiversity specialists, quarantine and border control personnel, educators and students, and other individuals and organizations concerned with the environment.

The GISD has recently launched two new initiatives: the Global Register of Invasive Species (GRIS) and the Global Management Project Register (GMPR).21 The GRIS will identify species with a history of being invasive by integrating invasive alien species checklist data generated by collection and observation databanks around the world. The GMPR will have case studies about prevention, eradication, control, and containment and mitigation activities.

Fortunately, those working on invasive species exhibit a willingness to share information and knowledge because they understand its importance for improving biodiversity outcomes. The GISD is just one of many responses to the need to collect and disseminate accurate, up-to-date, relevant information about invasive species. As awareness grows, people and communities are able to make informed choices that will have lasting effects on their descendants.

According to IUCN–The World Conservation Union, in its latest assessment of the state of life on our planet, the number of known threatened species reached 16,118 in 2006.1 The ranks of those already facing extinction were joined by familiar species like the hippopotamus and desert gazelles, along with ocean sharks, freshwater fish, and Mediterranean flowers.2 By now, 784 species on Earth have been declared extinct, and a further 65 are found only in captivity or cultivation.3

Of the 40,168 species assessed using the IUCN Red List criteria, one in three amphibians, a quarter of the world’s coniferous trees, one in eight birds, and nearly one in four mammals are now known to be in jeopardy.4 (See Table 1.) The term “threatened” includes three Red List categories of escalating threat: vulnerable, endangered, and critically endangered.

These numbers from the 2006 IUCN Red List of Threatened Species demonstrate the ongoing decline of global biodiversity and the impact that humankind is having on life on Earth. Additions to the list in 2006 included a particularly familiar face—the polar bear. This charismatic mammal is now classified as vulnerable, as it is set to become one of the most notable casualties of Earth’s rising temperature. The impact of climate change is increasingly felt in polar regions, where summer sea ice is expected to decrease by 50–100 percent over the next 50–100 years.5 Polar bears are predicted to suffer more than a 30-percent population decline in the next 45 years as the ice floes they depend on when they hunt seals slowly disappear.6

Escalating threats to desert wildlife are unregulated hunting and habitat degradation. The dama gazelle of the Sahara, which was listed as endangered in 2004, has suffered an 80-percent crash in numbers over the past 10 years because of uncontrolled hunting and is now deemed critically endangered.7 Other Saharan gazelle species are also threatened and seem destined to suffer the fate of the scimitarhorned oryx: extinct in the wild.8

In 2006, the Red List also included comprehensive regional assessments of selected marine groups. Sharks and rays are among the first such groups to be systematically assessed; of the 547 species evaluated so far, 20 percent are threatened with extinction.9 This confirms suspicions that these mainly slow-growing species are extremely susceptible to overfishing and are disappearing at an unprecedented rate.

The plight of the angel shark and common skate, once familiar sights in European fish markets, illustrates dramatically the recent rapid deterioration of many sharks and rays. They have all but disappeared from sale.10 The angel shark (moved from vulnerable to critically endangered) has been declared extinct in the North Sea, and the common skate (moved from endangered to critically endangered) is now very scarce in the Irish Sea and the southern North Sea.11

Freshwater species are not faring much better. They have suffered some of the most dramatic declines: 56 percent of the 252 endemic freshwater Mediterranean fish are threatened with extinction, the highest proportion in any regional freshwater fish assessment so far.12 Seven species, including carp relatives Alburnus akili in Turkey and Telestes ukliva from Croatia, are now extinct.13 Of the 564 dragonfly and damselfly species so far assessed, nearly one in three are threatened, including nearly 40 percent of endemic Sri Lankan dragonflies.14

Larger freshwater species, such as the common hippopotamus, are also in difficulty. One of Africa’s best known aquatic icons, it has been listed as threatened for the first time and is classified as vulnerable, primarily because of a catastrophic decline in the number of hippos in the Democratic Republic of the Congo.15 In 1994 this country had the second largest hippo population in Africa—30,000 after Zambia’s 40,000—but today numbers have plummeted by 95 percent due to unregulated hunting for meat and the ivory in hippo teeth.16

The IUCN Red List of Threatened Species has become an increasingly powerful tool for conservation planning, management, monitoring, and decision-making. It is used by government agencies and nongovernmental organizations in at least 57 countries to compile national Red Lists and is a focus for conservation action.17

Against the catalogue of decline, the latest data also show that conservation action does work. Following signifi- cant recoveries in many European countries, the numbers of whitetailed eagles doubled in the 1990s, and this species has been moved from the near threatened category to of least concern.18 Enforcement of legislation to protect the species from being killed and measures to address threats from habitat changes and pollution have resulted in increasing populations.19

On Australia’s Christmas Island, the seabird Abbott’s booby was declining due to habitat clearance and an introduced invasive alien species, the yellow crazy ant, which had a major impact on the island’s ecology.20 The booby, listed as critically endangered in 2004, is recovering thanks to conservation measures and has now been moved to the endangered category.21

Other plants and animals highlighted in previous Red List announcements as under threat are now the focus of concerted conservation actions, which it is hoped will improve their conservation status in the near future. Some noteworthy examples are the 300-kilogram Mekong catfish of Southeast Asia, the Indian vulture, the humphead wrasse, and the Saiga antelope.22

These examples also illustrate a valuable lesson: bringing about the recovery of species on the edge of extinction is much more difficult and costly than preventing the decline in the first place by, for example, protecting habitat. They also underline the need for reliable scientific data on the status of species to guide recovery efforts and for quicker responses by governments and civil society when species or habitats come under threat.

In its 2007 report, the Intergovernmental Panel on Climate Change (IPCC) left no doubt that global warming is occurring and that climate change is human-induced, concluding that “warming of the climate system is unequivocal” and stating with 90 percent confidence that the net effect of human activities on Earth since 1750 has been warming.1 And it is increasingly clear that this warming climate is having significant impacts on the world’s biodiversity.

In 2005 the Millennium Ecosystem Assessment (MA), which involved 1,360 scientists from 95 countries, concluded that climate change has affected biodiversity in all ecosystems over the last century, though the magnitude of the changes varied across ecosystem types.2 (See Table 1.)

The most studied and best understood impact is phenological changes, which are alterations in the timing of periodic biological events, such as the onset of animal migration or plant blooming, in response to climatic conditions. These events are typically linked to climate and are predicted to occur increasingly early in response to Earth’s steady warming; unfortunately, an increasing number of scientific studies present evidence consistent with this prediction. In plants, for instance, the flowering of cherry trees at the Royal Court in Kyoto, Japan, for which records have been maintained for at least 600 years, has advanced steadily since 1952.3 And in the western United States, the flowering of lilacs and honeysuckles has advanced by 2 and 3.8 days per decade, respectively. 4 Increased warming has also extended the growing season of some plants, as in the eastern deciduous forest of the United States, where the growing season has lengthened most notably since 1966, and in the colder, most northerly zones at 42°–45° latitude.5

Among invertebrate animals, a study of 35 butterfly species in the United Kingdom found that the date of first appearance for 26 species has grown earlier by between 1.0 and 15.8 days per decade between 1976 and 1998, while for the remaining 9 species it either has not changed (2 species) or has gotten later by between 0.1 and 3.6 days per decade.6 Likewise, between 1988 and 2002, the dates of first appearance for 17 Spanish butterfly species have advanced, as have the dates of first flight for 16 of 23 butterfly species in central California over 31 years.7 In vertebrate animals, studies have documented that the males of four American frog species are initiating calling 10–13 days earlier than before and that migrant birds in the North Sea have been passing 0.5–2.8 days earlier per decade since 1960.8 Other studies of birds have shown significant advances in the onset of breeding: by over eight days from 1971 to 1995 in 20 of 63 European bird species and by nine days from 1959 to 1991 for North American tree swallows.9 In a third study, of 23 European pied flycatcher populations, there was a significant correlation between changes in the local spring temperature and the onset of egg-laying—the warmer the local temperature, the earlier the onset of egg-laying within the local population.10

A second category of climate change effects are shifts in the range of a species, with movement in the long term expected to be toward each pole and to higher altitudes.11 Once again, a growing body of scientific evidence supports this. Near Antarctica, for instance, data indicate that several species of penguins, both sea ice–dependent and ocean-going species, have moved southward toward the pole.12 Among more temperate birds, data indicate that 12 species in the United Kingdom have moved northward by, on average, 18.9 kilometers over 20 years.13 Among insects, 23 species of dragonflies and damselflies in the United Kingdom expanded their ranges northward by on average 88 kilometers between 1960 and 1995.14

Cases of elevational shifts are also well documented. Among 16 Spanish butterflies, the lower elevational range has risen by, on average, 212 meters over 30 years.15 In mammals, 7 of the 25 populations of the pika in the western United States have gone extinct since being recorded in the 1930s, but the populations that disappeared were at significantly lower elevations than those that survived.16

These numerous studies indicate quite clearly that climate change has had a significant effect on terrestrial biodiversity, causing signifi- cant changes in a number of organisms across a wide array of ecosystems. Will these changes continue? And what will be their long-term effects? The IPCC and MA reports address the first of these questions. The IPCC concluded that it is “virtually certain” that recent warming trends will continue, and the MA projected that the impacts of climate change on biodiversity across all ecosystems will increase very rapidly.17

Answers to the second question are less clear. In some cases, the economic effects of climate change are likely to be positive; longer growing seasons and range shifts for agricultural crops benefit farmers in certain geographic regions, for example. Yet many of the impacts will be negative, including the direct and indirect effects of species relationships being disrupted and direct species extinctions.18 One study that synthesized the changes of 11 multispecies interactions found that more than 60 percent of the interactions had been disrupted and become less synchronous over time due to the different responses of individual species to climate change, producing, in some cases, significant negative consequences.19 Habitat loss and other climate change effects can also result in significant population declines. Polar bears, for instance, are dealing with decreases in the extent and thickness of sea ice, resulting in both shrinking population sizes and reductions in mean body weight.20 Thus climate change can significantly increase the probability of species extinction.

These individual accounts clearly demonstrate specific effects that climate change is having on terrestrial biodiversity. The larger scope of the problem is better illustrated by the IPCC, however. In an assessment of 29,000 observed changes in terrestrial biological systems, more than 89 percent of the significant changes were consistent with the direction of change expected as a response to global warming.21 The IPCC concluded “with high confidence that anthropogenic warming over the last three decades has had a discernible influence on many physical and biological systems.”22 Some of these changes are likely to have, at least in the short term, positive economic and biological impacts. But many of the long-term impacts will undoubtedly be negative. Among the most significant of those are a 5 out of 10 chance of an increased extinction risk for 20–30 percent of plants and animals and an 8 out of 10 chance of major changes in ecosystem structure and function.23

With increased understanding of the longterm consequences of climate change and the greater probability of negative biological outcomes should climate change continue at its current rate, the need to grapple with the challenges of global climate change also increases. The IPCC noted that a wide array of technological, behavioral, managerial, and policy options are currently available; however, they also noted that more extensive action is required in order to reduce human vulnerability to future climate change.24 As Tom Lovejoy of the Heinz Center for Science, Economics, and the Environment puts it, “Life on Earth is sending an urgent warning signal that climate change needs to be engaged with—and with an urgency and scale hitherto not contemplated.”25

After experiencing severe losses between 1979 and 1996, Earth’s ozone layer has ceased its precipitous decline, according to scientists with the U.S. National Oceanic and Atmospheric Administration.1 The average amount of ozone in the stratosphere in 2002–05 was similar to the average measured in 1998–2001, although it was still 3.5 percent below 1964–80 averages.2 (See Figure 1).

Meanwhile, at its annual peak, the “hole” in the ozone layer above Antarctica grew to 27.5 million square kilometers in 2006—close to the 28.7 million square kilometers reached in 2000.3 (See Figure 2.) Severe ozone losses are expected there for at least two more decades.4

The ozone layer protects Earth from harmful ultraviolet (UV) radiation by absorbing many of the sun’s UV rays. But the release into the atmosphere of certain chemicals, such as chlorofluorocarbons (CFCs) and methyl bromide, disrupts the ozone creation cycle, thinning this delicate shield. CFCs have been widely used for refrigeration purposes, aerosol propellants, and blowing agents.

In humans, high levels of UV radiation can cause sunburn and malignant melanoma, lesions and cataracts, and suppression of the immune system; in plants, they can cause DNA damage.5 When the Antarctic ozone hole widens, people in southern Chile and Argentina are advised to avoid direct sunlight to minimize their health risks.6

Much of the success in stabilizing atmospheric ozone levels can be attributed to the Montreal Protocol on Substances That Deplete the Ozone Layer, a treaty adopted in 1987 to reduce the release of ozone-depleting substances (ODS). As a result of scheduled ODS phaseouts in industrial and developing countries, CFC use decreased 96 percent between 1986 and 2005, to 41,200 tons, while methyl bromide use dropped to some 12,500 tons from 37,000 tons in 1995.7 (See Figure 3.) ODS persist in the stratosphere for many years, however, so decreased use does not immediately mean decreased accumulation. Meanwhile, use of hydrochlorofluorocarbons, a less-damaging CFC substitute that still contributes to some ozone loss, increased steadily— from less than 15,000 tons in 1992 to nearly 32,000 tons in 2005.8

Roughly 90 percent of the ozone in the atmosphere is found in the stratosphere, from 10–16 to 50 kilometers above Earth’s surface; the rest occurs in the troposphere (from the surface to 10–16 kilometers above).9 By 2005, total ODS levels in the troposphere had dropped 8–9 percent from their peak in 1992–94; though stratospheric ODS levels peaked in the late 1990s, reductions there are somewhat less because it takes a few years for near-surface trends to be reflected.10 The stabilization of the ozone layer has stopped the rise in surface UV radiation in unpolluted areas outside the poles and in some areas led to a slight decline in radiation.11

Production and use of harmful ODS has not ended completely, however. Exemptions for some ODS, such as methyl bromide for agricultural purposes, are slowing progress.12 Other challenges include the ongoing illegal trade in CFCs, growing legal production of ODS in developing countries, and the continued use of older refrigerators and other products that contain the chemicals.13

The consensus of most researchers is that ozone concentrations over Earth’s non-polar regions will return to pre-1980 levels between 2040 and 2050.14 Ozone concentrations over the Arctic are expected to reach pre-1980 levels at the same time or earlier, while those over the Antarctic are unlikely to do so until 2060–75 (and that is assuming continuing phaseout of ODS).15 The ozone hole is expected to remain large for at least a decade or so and will continue to fluctuate with meteorological conditions (it is larger in colder winters, for instance).16

Cyclic changes in UV radiation emitted by the sun affect ozone levels, since radiation initiates stratospheric ozone formation.17 A typical solar cycle can contribute to a 1–2 percent variation in total ozone levels.18 Volcanic eruptions deplete the ozone layer as well, by emitting large amounts of sulfur dioxide, which convert to aerosols that aid chlorine destruction of ozone.19 Neither of these factors, however, plays as large a role in ozone stability as the release of ODS does.20