Ecosystems and land use

Land use is the human use of land.   Land use involves the management and modification of natural environment or wilderness into built environment such as fields, pastures, and settlements. It also has been defined as "the arrangements, activities and inputs people undertake in a certain land cover type to produce, change or maintain it" Land use practices vary considerably across the world. The United Nations' Food and Agriculture Organization Water Development Division explains that "Land use concerns the products and/or benefits obtained from use of the land as well as the land management actions (activities) carried out by humans to produce those products and benefits." As of the early 1990s, about 13% of the Earth was considered arable land, with 26% in pasture, 32% forests and woodland, and 1.5% urban areas.

Land use and land management practices have a major impact on natural resources including water, soil, nutrients, plants and animals. Land use information can be used to develop solutions for natural resource management issues such as salinity and water quality. For instance, water bodies in a region that has been deforested or having erosion will have different water quality than those in areas that are forested. Forest gardening, a plant-based food production system, is believed to be the oldest form of land use in the world.

The major effect of land use on land cover since 1750 has been deforestation of temperate regions. More recent significant effects of land use include urban sprawl, soil erosion, soil degradation, salinization, and desertification. Land-use change,  together with use of fossil fuels, are the major anthropogenic sources of carbon dioxide, a dominant greenhouse gas.

According to a report by the United Nations' Food and Agriculture Organisation, land degradation has been exacerbated where there has been an absence of any land use planning, or of its orderly execution, or the existence of financial or legal incentives that have led to the wrong land use decisions, or one-sided central planning leading to over-utilization of the land resources - for instance for immediate production at all costs. As a consequence the result has often been misery for large segments of the local population and destruction of valuable ecosystems. Such narrow approaches should be replaced by a technique for the planning and management of land resources that is integrated and holistic and where land users are central. This will ensure the long-term quality of the land for human use, the prevention or resolution of social conflicts related to land use, and the conservation of ecosystems of high biodiversity value.

Urban growth boundaries

The urban growth boundary is one form of land-use regulation. For example, Portland, Oregon is required to have an urban growth boundary which contains at least 20,000 acres (81 km²) of vacant land. Additionally, Oregon restricts the development of farmland. The regulations are controversial, but an economic analysis concluded that farmland appreciated similarly to the other land.

Impacts

Unchecked global warming could affect most terrestrial ecoregions. Increasing global temperature means that ecosystems will change; some species are being forced out of their habitats (possibly to extinction) because of changing conditions, while others are flourishing. Secondary effects of global warming, such as lessened snow cover, rising sea levels, and weather changes, may influence not only human activities but also the ecosystem.

For the IPCC Fourth Assessment Report, experts assessed the literature on the impacts of climate change on ecosystems. Over the last three decades, human-induced warming had likely had a discernable influence on many physical and biological systems. Schneider et al. (2007) concluded, with very high confidence, that regional temperature trends had already affected species and ecosystems around the world. Climate change would result in the extinction of many species and a reduction in the diversity of ecosystems.

• Terrestrial ecosystems and biodiversity: With a warming of 3°C, relative to 1990 levels, it is likely that global terrestrial vegetation would become a net source of carbon (Schneider et al., 2007:792). With high confidence, Schneider et al. (2007:788) concluded that a global mean temperature increase of around 4°C (above the 1990-2000 level) by 2100 would lead to major extinctions around the globe.
• Marine ecosystems and biodiversity: With very high confidence, Schneider et al. (2007:792) concluded that a warming of 2°C above 1990 levels would result in mass mortality of coral reefs globally.
• Freshwater ecosystems: Above about a 4°C increase in global mean temperature by 2100 (relative to 1990-2000), Schneider et al. (2007:789) concluded, with high confidence, that many freshwater species would become extinct.

Studying the association between Earth climate and extinctions over the past 520 million years, scientists from the University of York write, "The global temperatures predicted for the coming centuries may trigger a new ‘mass extinction event’, where over 50 per cent of animal and plant species would be wiped out"

Many of the species at risk are Arctic and Antarctic fauna such as polar bears and Emperor Penguins. In the Arctic, the waters of Hudson Bay are ice-free for three weeks longer than they were thirty years ago, affecting polar bears, which prefer to hunt on sea ice. Species that rely on cold weather conditions such as gyrfalcons, and Snowy Owls that prey on lemmings that use the cold winter to their advantage may be hit hard. Marine invertebrates enjoy peak growth at the temperatures they have adapted to, regardless of how cold these may be, and cold-blooded animals found at greater latitudes and altitudes generally grow faster to compensate for the short growing season. Warmer-than-ideal conditions result in higher metabolism and consequent reductions in body size despite increased foraging, which in turn elevates the risk of predation. Indeed, even a slight increase in temperature during development impairs growth efficiency and survival rate in rainbow trout.

Rising temperatures are beginning to have a noticeable impact on birds, and butterflies have shifted their ranges northward by 200 km in Europe and North America. Plants lag behind, and larger animals' migration is slowed down by cities and roads. In Britain, spring butterflies are appearing an average of 6 days earlier than two decades ago.

A 2002 article in Natur surveyed the scientific literature to find recent changes in range or seasonal behaviour by plant and animal species. Of species showing recent change, 4 out of 5 shifted their ranges towards the poles or higher altitudes, creating "refugee species". Frogs were breeding, flowers blossoming and birds migrating an average 2.3 days earlier each decade; butterflies, birds and plants moving towards the poles by 6.1 km per decade. A 2005 study concludes human activity is the cause of the temperature rise and resultant changing species behaviour, and links these effects with the predictions of climate models to provide validation for them. Scientists have observed that Antarctic hair grass is colonizing areas of Antarctica where previously their survival range was limited. Two populations of Bay checkerspot butterfly being threatened by precipitation change.

Many species of freshwater and saltwater plants and animals are dependent on glacier-fed waters to ensure a cold water habitat that they have adapted to. Some species of freshwater fish need cold water to survive and to reproduce, and this is especially true with Salmon and Cutthroat trout. Reduced glacier runoff can lead to insufficient stream flow to allow these species to thrive. Ocean krill, a cornerstone species, prefer cold water and are the primary food source for aquatic mammals such as the Blue Whale. Alterations to the ocean currents, due to increased freshwater inputs from glacier melt, and the potential alterations to thermohaline circulation of the worlds oceans, may affect existing fisheries upon which humans depend as well.

The white lemuroid possum, only found in the Daintree mountain forests of northern Queensland, may be the first mammal species to be driven extinct by global warming in Australia. In 2008, the White Possum has not been seen in over three years. The possums cannot survive extended temperatures over 30 °C (86 °F), which occurred in 2005.

A 27-year study of the largest colony of Magellanic penguins in the world, published in 2014, found that extreme weather caused by climate change is responsible for killing 7% of penguin chicks per year on average, and in some years studied climate change accounted for up to 50% of all chick deaths. Since 1987, the number of breeding pairs in the colony has reduced by 24%.

Forests

Pine forests in British Columbia have been devastated by a pine beetle infestation, which has expanded unhindered since 1998 at least in part due to the lack of severe winters since that time; a few days of extreme cold kill most mountain pine beetles and have kept outbreaks in the past naturally contained. The infestation, which (by November 2008) has killed about half of the province's lodgepole pines (33 million acres or 135,000 km²) is an order of magnitude larger than any previously recorded outbreak. One reason for unprecedented host tree mortality may be due to that the mountain pine beetles have higher reproductive success in lodgepole pine trees growing in areas where the trees have not experienced frequent beetle epidemics, which includes much of the current outbreak area. In 2007 the outbreak spread, via unusually strong winds, over the continental divide to Alberta. An epidemic also started, be it at a lower rate, in 1999 in Colorado, Wyoming, and Montana. The United States forest service predicts that between 2011 and 2013 virtually all 5 million acres (20,000 km²) of Colorado’s lodgepole pine trees over five inches (127 mm) in diameter will be lost.

As the northern forests are a carbon sink, while dead forests are a major carbon source, the loss of such large areas of forest has a positive feedback on global warming. In the worst years, the carbon emission due to beetle infestation of forests in British Columbia alone approaches that of an average year of forest fires in all of Canada or five years worth of emissions from that country's transportation sources.

Besides the immediate ecological and economic impact, the huge dead forests provide a fire risk. Even many healthy forests appear to face an increased risk of forest fires because of warming climates. The 10-year average of boreal forest burned in North America, after several decades of around 10,000 km² (2.5 million acres), has increased steadily since 1970 to more than 28,000 km² (7 million acres) annually. Though this change may be due in part to changes in forest management practices, in the western U.S., since 1986, longer, warmer summers have resulted in a fourfold increase of major wildfires and a six fold increase in the area of forest burned, compared to the period from 1970 to 1986. A similar increase in wildfire activity has been reported in Canada from 1920 to 1999.

Forest fires in Indonesia have dramatically increased since 1997 as well. These fires are often actively started to clear forest for agriculture. They can set fire to the large peat bogs in the region and the CO₂ released by these peat bog fires has been estimated, in an average year, to be 15% of the quantity of CO₂produced by fossil fuel combustion.

Mountains

Mountains cover approximately 25 percent of earth's surface and provide a home to more than one-tenth of global human population. Changes in global climate pose a number of potential risks to mountain habitats. Researchers expect that over time, climate change will affect mountain and lowland ecosystems, the frequency and intensity of forest fires, the diversity of wildlife, and the distribution of water.

Studies suggest that a warmer climate in the United States would cause lower-elevation habitats to expand into the higher alpine zone. Such a shift would encroach on the rare alpine meadows and other high-altitude habitats. High-elevation plants and animals have limited space available for new habitat as they move higher on the mountains in order to adapt to long-term changes in regional climate.

Changes in climate will also affect the depth of the mountains snow packs and glaciers. Any changes in their seasonal melting can have powerful impacts on areas that rely on freshwater runoff from mountains. Rising temperature may cause snow to melt earlier and faster in the spring and shift the timing and distribution of runoff. These changes could affect the availability of freshwater for natural systems and human uses.

Ecological productivity

•  The relationship between increased global mean temperature and ecosystem productivity is parabolic. Higher carbon dioxide concentrations will favourably affect plant growth and demand for water. Higher temperatures could initially be favourable for plant growth. Eventually, increased growth would peak then decline.
• According to IPCC (2007:11), a global average temperature increase exceeding 1.5–2.5°C (relative to the period 1980–99), would likely have a predominantly negative impact on ecosystem goods and services, e.g., water and food supply.
• Research done by the Swiss Canopy Crane Project suggests that slow-growing trees only are stimulated in growth for a short period under higher CO₂ levels, while faster growing plants like liana benefit in the long term. In general, but especially in rainforests, this means that liana become the prevalent species; and because they decompose much faster than trees their carbon content is more quickly returned to the atmosphere. Slow growing trees incorporate atmospheric carbon for decades.

Species migration

In 2010, a gray whale was found in the Mediterranean Sea, even though the species had not been seen in the North Atlantic Ocean since the 18th century. The whale is thought to have migrated from the Pacific Ocean via the Arctic. Climate Change & European Marine Ecosystem Research (CLAMER) has also reported that the Neodenticula seminae alga has been found in the North Atlantic, where it had gone extinct nearly 800,000 years ago. The alga has drifted from the Pacific Ocean through the Arctic, following the reduction in polar ice.

In the Siberian subarctic, species migration is contributing to another warming albedo-feedback, as needle-shedding larch trees are being replaced with dark-foliage evergreen conifers which can absorb some of the solar radiation that previously reflected off the snowpack beneath the forest canopy.

Global ecologist Jon Bergengren states that when plants and animals attempt to survive by shifting their geographical ranges, as they have in past episodes of climate change, they'll be blocked by farms and cities. "If half the world is driven to change its vegetation cover, and meanwhile, we've fragmented the surface of the Earth by putting in parking lots and monoculture agricultural zones and all these other impediments to natural migration, then there could be problems. When, suddenly, plants and animals aren't living in habitats to which they're adapted, then you start to get an unhealthy planet," he said.

 

Agriculture

                Droughts have been occurring more frequently because of global warming and they are expected to become more frequent and intense in Africa, southern Europe, the Middle East, most of the Americas, Australia, and Southeast Asia. Their impacts are aggravated because of increased water demand, population growth, urban expansion, and environmental protection efforts in many areas. Droughts result in crop failures and the loss of pasture grazing land for livestock.

Price of corn in North America, in U.S. dollars per bushel, 2004-2012

Droughts are becoming more frequent and intense in arid and semiarid western North America as temperatures have been rising, advancing the timing and magnitude of spring snow melt floods and reducing river flow volume in summer. Direct effects of climate change include increased heat and water stress, altered crop phenology, and disrupted symbiotic interactions. These effects may be exacerbated by climate changes in river flow, and the combined effects are likely to reduce the abundance of native trees in favor of non-native herbaceous and drought-tolerant competitors, reduce the habitat quality for many native animals, and slow litter decomposition and nutrient cycling. Climate change effects on human water demand and irrigation may intensify these effects. By 2012, North American corn prices had risen to a record $8.34 per bushel in August, leaving 20 of the 211 U.S. ethanol fuel plants idle.