Assessing primate exposure and vulnerability to climate change

Source: Graham, T. L., Matthews, H. D., & Turner, S. E. (2016). A global-scale evaluation of primate exposure and vulnerability to climate change. International Journal of Primatology37(2), 158-174.

Climate change could have catastrophic impacts on animal populations, in fact, I’d go as far to say that it’s a slow-moving extinction event. In response to this, organisations are trying to help as many species as possible – But how do you know which species is most vulnerable?

Of the studies that have assessed a species’ vulnerability to climate change, only a small minority have looked at non-human primates (NHP from now on). These are animals that act as flagship species for entire ecosystems and are already threatened by human activities such as deforestation, hunting and the exotic pet trade. The studies that have assessed vulnerability have identified two key factors that could seriously impact NHP populations: variations in temperature and/or precipitation. These factors also contribute to more serious scenarios such as drought, flooding and elevated temperatures.

The impacts of climate change on NHP are wide-ranging, varied and most certainly scary. These include:

  • Decreases in reproduction and/or survival
  • Decreased thermoregulatory capacity
  • Decreased quantity and quality of food supply
  • Changes in sex ratios
  • Increases in enforced resting time
  • Increased rates of predation and infanticide
  • Increases in parasitic infections and rates of disease transmission
  • Increased mortality
  • Increasing isolation of subpopulations due to upward altitudinal range shifts

On top of this, you also have the impact of more severe storm events and natural disasters. Hurricane Maria for example, removed 75% of the trees, 55% of shrubs and 100% of vines on Cayo Santiago (pictured below). The island is home to a population of rhesus macaques and Hurricane Maria essentially wiped out their food supply in a matter of days.

More worryingly, IUCN identifies 54% of world’s primate species as currently threatened with extinction. While these endangered species are found across the globe, the highest concentrations are of Endangered and Critically Endangered species are found in Central and South America, in West Africa and East and Southeast Asia.

It is expected that warming averaged across all primate ranges is 1.1°C per °C of global warming. Generally, this means primates will experience 10% more warming than the global mean. Of this increase, areas in continental interiors and those at higher altitudes will see more, whilst tropical coastal regions will see less. The largest increase in precipitation (>7.5% per °C of warming) is expected in Eastern Africa, while the largest decrease (>7.5% decrease per °C of warming) would be in Southern Africa and Central America.

It’s no surprise then species in Central America, portions of South America and the Amazon Basin, North and East Africa, and the Himalayan mountain range are expected to experience the most severe climate change effects. In particular, the Kashmir grey langur, Barbary macaque and the Tana River mangabey are expected to be exposed to very large climate change.

It’s easy to talk about climate change as just warmer temperatures, or more precipitation but it is so much more complex. It reduces a species’ range size by pushing them up to higher altitudes or changes the availability and phenology of specialised food resources.

The most critically endangered, more often than not, have small range sizes, specialised diets and need particular habitats to survive. These are the characteristics that can increase a species’ vulnerability to climate change.

Hotspots of primate vulnerability to global warming. Hotspot scores are calculated (per km2 ) as the product of normalized measures of species richness, average extinction risk, and climate change severity, and are classified here by quantile. The darkest colours represent the highest hotspot scores, and indicate locations of high species richness, where species are currently threatened by human pressures, and where these species are also expected to experience large changes in temperature and/or precipitation.

In my opinion, the most vulnerable species are those in Central and South America, West Africa and the Himalayan mountain range. These regions are home to the most endangered primates species, and are also the regions that will experience the most extreme climate change.

62.6% of primate species are projected to experience temperature increases of greater than the global mean, but it is the species in these regions that will be hit hardest. That’s why we need to target these areas with research first.

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