Climate Change and Extinctions on Mountain Summits

The complex topography of the andes mountain range restricts the altitudinal movements that species may have in response to climate change. This phenomenon could increase the number of threatened species in tropical mountains and cause extinctions.

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Possible movements of species to higher elevations

PRESENT

Pristimantis sanctaemartae¹

FUTURE

(1) Altitudinal movement of ranges to lower summits (future thermal traps); (2) Movement towards a thermal trap (3) Movement of range towards unsuitable land covers

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One of the responses of species to global climate change is the movement of altitudinal ranges to greater elevations^1,2. This phenomenon is of special importance in the tropical region, where the latitudinal gradient of temperature is not marked, so attaining lower temperatures in order to maintain optimal conditions is achieved by ascending in altitude.

Many tropical species have reduced altitudinal ranges and thermal tolerances. As local temperatures increase, many of these species will not be able to survive unless they move to greater altitudes. Species of insects, birds, and amphibians have already started to move upwards in tropical mountains^3,^4,⁵.

Two possible effects of altitudinal movements of species are reduced ranges and extinction. The reduction of ranges is caused by restrictions due to topography and inadequate land covers such as urban areas, crops, or barren land⁶. More specifically, it may be the case that some individuals move to higher elevations inside their current range, but these areas would become isolated if warming continues, preventing individuals to reach higher elevations and causing a possible reduction in the area of distribution.

Extinction would affect those species that inhabit areas closest to mountain summits and reduced altitudinal ranges. As temperature isoclines move upwards, the current environment they inhabit, in terms of temperature, could disappear. This implies habitat reduction or loss, which in turn may cause extinctions. These type of extinctions are also known as mountain summit extinctions².

The two scenarios mentioned above are effects of global climate change. In complex landscapes such as the Andes mountains connectivity along altitudinal gradients should be maintained to ensure species movement and reduce pressures on those species that inhabit mountain summits.

▲ Case: Amphibians ▼

Case study

Distribution reduction and isolation for amphibians in the sierra nevada de Santa Marta

Amphibians are one of the groups that may be mostly affected by restrictions of altitudinal movements and isolation of parts of their distribution. In the Sierra Nevada de Santa Marta, an area that has more than 15 endemic species of amphibians, the complexity of the topography and transformation of land covers will impact altitudinal movements of amphibians. For 21 out of the 46 studied species, 30 % of the current range will move to areas of low relief that will become isolated as temperature increases. Three of these species are endemic. For 13 of the species studied, including an endemic one, 30 % of the current distribution will move to unsuitable areas such as crops or urban areas. For 7 species, more than 70 % of the range can be reduced as temperature increases.

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Ikakogi tayrona

Movements in ranges of Ikakogi tayrona

Current range New area
Area that overlaps with current range Areas of thermal isolation

Changes in the range of this amphibian species to higher elevations under four different scenarios of increasing temperatures are shown. As the species moves upwards, areas of thermal isolation towards which animals move to find colder temperatures are evidenced. Eventually, these areas become inadequate for the survival of the species.

◀ Case: Birds ▼

Case study

Summit extinctions in birds

Pirre Warbler

Under the scenario of an increase in temperature of 2ºC, which corresponds to a 364 m.a.s.l. escalation of isoclines, no bird species would move its range completely or be in imminent risk of extinction. On the other hand, if temperature increases by 5ºC isoclines would move 909 meters upwards; therefore, the habitat of five bird species would completely disappear, potentially causing extinction. These five species are: Basileuterus ignotus, Asthenes perijana, Odontophorus dialeucus, Chlorostilbon olivaresi y Tangara fucosa. All possible extinctions would occur in relatively isolated mountains of low elevation such as Darién, Perijá, and Chiribiquete.

▲ Map ▶

Altitudinal movements of Basileuterus ignotus in the Serranía del Darién Basileuterus ignotus del Darién

The polygon shows changes in distribution as temperature increases 2ºC and 5ºC. The movement of the species equals 40 % of the movement of temperature isoclines. If temperature increases by 5ºC and the species movements equals that of the isoclines, the current temperatures of the species’ range would disappear, potentially causing a summit extinction.

◀ Case: Birds ▼