Adaptation (1)

Introduction

 An adaptation to climate change is any adjustment in a natural or human system that decreases the harm caused by climate change or takes advantage of some opportunity it offers.

Both natural and human systems may adapt to actually occurring climate change; humans are unique in being able to forecast changes and attempt to adapt to them in a planned way.There are three types of adaptation, namely anticipatory, autonomous, and planned. Anticipatory adaptation takes place before predicted impacts are observed; autonomous or spontaneous adaptation takes place in direct response to ecological or economic impacts of climate change; and planned adaptation is based on deliberate policy decisions. How much adaptation will occur depends on several factors, including how much climate changes, how severe the impacts of that change are, where they are most severe, how adaptable impacted ecosystems and human communities are, andwhether effective policies are followed for mitigating and adapting to climate impacts.

Some impacts of climate change are already being felt, and some adaptation by both natural and human systems has already begun.However, adaptation is not always possible.

For ecosystems, failure to adapt means the collapse of existing ecologies and their replacement by others, along with species extinctions. For human communities, failure to adapt means partial or severe breakdown of existing ways of life, with consequences ranging from monetary losses to famine and mass death. In general, slower climate change is easier to adapt to than sudden change, and slight change is easier to adapt to than extreme change.

 Historical Background and Scientific Foundations

 Natural and Historic Adaptation

 Over geologic time, Earth’s climate has changed regionally and globally many times. Ice ages have spanned millions of years, dotted by glacial and interglacial cycles; the sun has gradually warmed throughout life’s history; carbon dioxide (CO2) concentrations were far higher than todays during most of Earth’s history; and regional shifts in rainfall patterns and temperature have been common. Adaptation by natural systems-or failure to adapt, on a few occasions leading to mass extinctions involving the majority of living species-has thus always been a feature of life on Earth.

Since the evolution of human beings, regional and local climate changes have continued to occur, though not with the intensity of the most drastic changes of the deep past. Some climate changes, such as the El Niño-Southern Oscillation climate cycle, occur regularly and last for years, and adaptation to them is routine in affected parts of the world. Affected ecosystems and peoples have, historically, sought to adapt to climate changes, often successfully.

Most plants and animals are evolved to thrive in a certain range of climate conditions: too little or too much precipitation or warmth are not tolerable to them.Therefore no species is found everywhere on Earth, but only where climate conditions are favorable and where the species has managed to cross geographical barriers to colonize a given area. For example, the European downy birch, a tree species, requires cold temperatures. It thrives in northern Asia and Europe and is the only tree native to Greenland and Iceland; it is not found in tropical areas, even in high mountainous zones where it might be able to survive if its seeds could reach those locations.

Natural adaptation for plants consists mostly of range shifting. As global warming proceeds, a plant such as the European downy birch will gradually cease to be found in the southernmost parts of its historical range and will seed itself northward to areas that were formerly too cold. Since plants and animals tend to live in adapted communities, with animals depending on particular plants and vice versa, entire biomes (types of habitat) will shift location as climate changes, plants and animals together. Such shifts may happen quickly, on the scale of a human lifetime: range shifts have already been measured in many parts of the world.

For mountainous species, as warming causes cold climate zones to move to higher altitudes, habitats move upward and shrink. For example, the uppermost altitude for pine mistletoe in Switzerland was 656 ft (200 m) higher in 2004 than it was in 1910. Range shifts can also occur more slowly. In North America, almost all of present-day Canada was covered by ice about 21,000 years ago, and spruce trees were found across what is now the northern and central United States, down into Texas and the Southwest.

Over the next 15,000 years, spruce forests migrated northward as the ice retreated. By 7,000 years ago, spruce was common only in northern areas that had formerly been covered by ice. This pattern persists today, and modern climate change will drive spruce forests even farther north. Over longer time periods, adaptation may be genetic as well as geographic. However, evolving new climate tolerances is a far slower, chancier process than colonizing new regions. Failure to either migrate or evolve leads to extinction. Human history shows varying levels of adaptation to climate swings. For example, the world’s first civilized empire, the Akkadia, was established between 4300 and 4200 BC in Mesopotamia, that is, the plain between the Tigris and Euphrates rivers, much of which is located in what is Iraq today. After only about 100 years of prosperity, the empire collapsed. Soil cores from the region—cylinders of undisturbed soil extracted vertically from the ground—contain a layer of wind-blown silt that records a 300-year drought that began shortly before the Akkadian collapse. Archaeological evidence shows that the Akkadians tried to adapt to this change by building larger grain storage facilities and irrigation systems, but these adaptations were insufficient.

From paleoclimatic evidence, the Mesopotamian drought has been linked to a cooling event in the North Atlantic in which surface water temperatures declined by 1.8–3.6°F (1–2°C). Modern temperature records show that the year-to-year water supply of the Mesopotamian plain can be cut in half by unusual cooling of the Atlantic. Century-scale regional drought has also been implicated in the collapse of the classic Maya civilization around AD 800, along with overpopulation, deforestation, erosion, and war, and of the Tiwanaku culture in the Bolivian-Peruvian altiplano about AD 1000. The collapse of the urban and military structures of these societies can be viewed as a form of adaptation: inresponse to increased scarcity brought on by climate change, they reduced their social complexity, abandoned cities, and reorganized their systems of production and supply. In all cases, human populations persisted, though decreased in number. However, such forced, autonomous adaptation is painful and often deadly for individuals caught up in it.

The global warming being experienced today is unique in Earth’s history in that it is caused by human beings. Today’s concern with anticipatory, planned adaptation to human-caused (anthropogenic) climate change is also a historical first. Not until the late twentieth century did humans understand the causes of climate change and possess the ability to make reasonably reliable predictions of its future course. The scientific study of adaptation to sea-level rise and the other effects of climate change began in the late 1980s and early 1990s, when extensive studies of adaptation strategies began to appear.

Modern adaptation, whether autonomous (reacting to existing changes) or anticipatory, will be based on the impacts of climate change. Hundreds of these potential impacts have been studied and many are being observed already, including rising sea levels, shifts in rainfall, increased heat waves, migrations of biomes (regional ecosystems), bleaching of corals, and many more. Impacts are often outlined by geographic region or by sector.

Freshwater Resources

Projected increases in air temperature, variability of rainfall, and sea level will impact freshwater systems in many parts of the world during the coming centuries. Over 16% of the world’s population lives in basins fed by glacial melt or snowmelt flows, which will decline as warming shrinks glaciers, decreases precipitation in some areas, and shortens snow seasons. Rising sea level will extend salty water inland by penetrating groundwater aquifers, which will reduce freshwater availability for communities in coastal zones. Increased precipitation in some areas will increase flooding risk; decreased precipitation in others will increase drought risk. Adaptations to impacts on freshwater resources can be either supply-side or demand-side. Supply-side adaptations seek to ensure supplies, while demand-side adaptations seek to reduce usage, allowing communities to prosper even when supplies decrease. Some supply-side adaptations include desalination of seawater, increasing storage capacity by building reservoirs, and expanding rainwater storage systems. Some demand-side adaptations include water recycling to increase water-use efficiency, reducing irrigation demands by changing crop mixes, planting calendars, irrigation methods, and providing incentives for water conservation such as metering and pricing.

 Ecosystems

 Increased atmospheric CO2, along with the warming that it causes, will affect most ecosystems in the coming century and for long after. By the end of the twenty-first century, atmospheric CO2 exceeds levels seen for at least 650,000 years. Even apart from warming,CO2 has direct ecosystem effects, speeding the growth of terrestrial plants and making the oceans significantly more acidic. Some 20–30% of plant and animal species that had been specifically examined as of 2005 in an unbiased (random) sample were likely to be at increased extinction risk as the world warms by 3.6–5.4°F (2–3°F C) above pre-industrial (pre–1750) levels.

Adaptations to impacts on ecosystems can be both natural and human. Natural adaptations will consist mostly of biome migration. Human responses will involve changes in management of natural resources and wild areas. There are a number of ways that human managers can increase the resilience of ecosystems, though these will likely become less effective or outright useless at higher levels of climate change. First, monitoring changes in climate and ecosystems is essential to allow for effective adjustments in management.

Reducing harm to natural systems by other human activities-including pollution, habitat destruction, habitat fragmentation (where development and habitat destruction break up habitats into isolated pieces), and the introduction of invasive alien species-will almost always enhance the ability of ecosystems to adapt to climate change. Expansion of national forests and parks and other kinds of reserve systems will reduce ecosystem vulnerability to climate change, especially if reserves are designed to consider long-term migrations of biomes and human settlements. For particular species, managing for connected populations (rather than isolated pockets of population), genetic diversity, and larger populations will increase survivability in response not only to climate change but to other challenges.

 Agriculture and Forestry

 In some mid-latitude and northerly regions, moderate global warming that is, warming of 1.8–5.4°F (1–3°C)—is likely to benefit agriculture by increasing yields from pastures and crops. However, even mild warming will decrease yields in low-latitude regions, including the tropics, where most of the world’s poor live. Higher levels of warming, which are quite possible, will have negative impacts on agriculture in all regions.

Although United Nations scenarios for possible world development show the number of malnourished persons in the world declining from about 820 million today to 100–380 million by 2080, this range is greater than it would be if global climate change were not occurring. Climate change also serves to shift the regional distribution of hunger, especially making hunger worse in sub-Saharan Africa. The productivity of commercial forestry is forecast to rise slightly to modestly in the short and medium term, partly due to the fertilizing affect of CO2 on young trees. There are many possible adaptive responses to climate change’s impacts on agriculture. These include altering the varieties or species planted to those better adapted to increased warmth or decreased rainfall, more efficient irrigation techniques, altering the timing and location of crop planting, and diversifying income generation (for example, by raising livestock). In a study of agricultural adaptation to hotter, drier summers in Modena, Italy, it was predicted that with unchanged farming practices sorghum crops would be reduced by 48–58%.With adjusted sorghum varieties and planting times, the impact could potentially be reduced to zero.

 Coastal Systems

 Rising sea levels and increased storm violence will impact coastal areas around the world. Over a billion people live in coastal areas today, with coastal population growing to over 5 billion by 2080 according to some global development scenarios. The 300 million people living on large river deltas-close to, at, or even below present-day sea level-will be particularly at risk for impacts, especially flooding. Sea level is predicted to rise by 2 ft (0.6 m) or more by 2100, and to continue rising thereafter.

Over the next several centuries to a millennium, complete melting of the Greenland and West Antarctic Peninsula ice sheets could raise sea levels by 40 ft (12 m), radically altering coastlines. Hurricanes and tropical cyclones will probably increase in intensity, and the effects of these intensified storms will be amplified by higher sea levels. Without improved coastal protection, coastal flooding could increase by a factor of 10 by the 2080s, affecting over 100 million people, mostly in developing countries.

Adaptations to the coastal impacts of climate change take three basic forms: protection, accommodation, or retreat. Protection is practically synonymous with the building of dikes to keep back the sea, as in Holland and New Orleans, Louisiana. Accommodation may include flood-resistant building construction (e.g., buildings on pilings) or floating agricultural systems (now being tested in Holland). Retreat essentially means moving settlements back to higher ground. Astute combination of various forms of these adaptation options could reduce the impacts of sea-level rise by 10 to 100 times in many areas; at the other extreme, as for small islands in the Pacific, no adaptation may be feasible, and ‘‘retreat’’ may have to signify abandonment.

 Human Health

 Climate change is projected to increase malnutrition; injure child growth and development; increase the number of people suffering death and disease from extreme weather events such as storms, droughts, heat waves, and floods; shift the ranges of some infectious disease vectors; increase the amount of diarrheal disease (which presently causes 5–8 million deaths per year, mostly children); increase cardio-respiratory disease due to ground-level ozone; and decrease the number of deaths from cold in northern regions. Hurricane Katrina (2005) showed that even highly developed countries such as the United States may not be well-prepared for the health and other consequences of extreme weather events.

Adaptations to the impacts of climate change on health will mostly take the form of revised policies and procedures of national and international health organizations (in the United States, for example, the Centers for Disease Control and Prevention – CDC). Climate-based early warning systems for heat waves and malaria outbreaks have already been implemented in some countries. Seasonal forecasts of events such as drought can allow the timely launching of public education campaigns on the prevention of diarrheal and other infectious diseases.

 Terms:

 Altiplano: High plateau region in the Andes of Argentina, Bolivia, and Peru in South America, the second-largest high plateau on Earth after Tibet. Sediments in Lake Titicaca, into which the Altiplano drains, record tens of thousands of years of regional climate change.

Biome: Well-defined terrestrial environment (e.g., desert, tundra, or tropical forest). The complex of living organisms found in an ecological region.

Deforestation: Those practices or processes that result in the change of forested lands to non-forest uses. This is often cited as one of the major causes of the enhanced greenhouse effect for two reasons: 1) the burning or decomposition of the wood releases carbon dioxide; and 2) trees that once removed carbon dioxide from the atmosphere in the process of photosynthesis are no longer present and contributing to carbon storage.

El Niño – Southern Oscillation: Global climate cycle that arises from interaction of ocean and atmospheric circulations. Every 2 to 7 years, westward-blowing winds over the Pacific subside, allowing warm water to migrate across the Pacific from west to east. This suppresses normal upwelling of cold, nutrient-rich waters in the eastern Pacific, shrinking fish populations and changing weather patterns around the world.

Geologic Time: The period of time extending from the formation of Earth to the present.

Glacial Cycle: Episode in Earth climate history in which temperatures decline and glaciers grow and spread, sometimes covering large parts of the northern and southern hemispheres. The most recent glacial cycle ended about 10,000 years ago.

Ice Age: Period of glacial advance.

Mangrove Forest: Coastal ecosystem type based on mangrove trees standing in shallow ocean water: also termed mangrove swamp. Mangrove forests support shrimp fisheries and are threatened by rising sea levels due to climate change.

Paleoclimate: The climate of a given period of time in the geologic past.

Range Shift: Movement or shrinkage of the territory occupied by a given species of plant or animal due to climate change. When climate warms, species cease to occupy areas that were at the warm extreme of their ability to adapt and to colonize areas that were at the cool extreme. The result is a shifting range.

River Delta: Flat area of fine-grained sediments that forms where a river meets a larger, stiller body of water such as the ocean. Rivers carry particles in their turbulent waters that settle out (sink) when the water mixes with quieter water and slows down; these particles build the delta. Deltas are named after the Greek letter delta, which looks like a triangle. Very large deltas are termed mega deltas and are often thickly settled by human beings. Rising sea levels threaten settlements on mega deltas.

 In Context: Abrupt Climate Change Happens

 According to the National Academy of Sciences of United States: ‘‘Evidence shows that the climate has sometimes changed abruptly in the past-within a decade-and could do so again. Abrupt changes, such as the Dust Bowl drought of the 1930s that displaced hundreds of thousands of people in the American Great Plains, take place so rapidly that humans and ecosystems have difficulty adapting to them.’’

Source: Staudt, Amanda, Nancy Huddleston, and Sandi Rudenstein. Understanding and Responding to Climate Change. National Academy of Sciences, 2006.