Wildlife & Biodiversity

COP28: Climate change having devastating impact on migratory species

Habitat loss, impact on reproduction, reduction in food availability among factors threatening migratory animal popualtions  

Himanshu Nitnaware
Published: Sunday 10 December 2023
Photo: iStock__

Climate change and biodiversity loss is having catastrophic impacts on many migratory species population, impacting their habitats, food availability and reproduction cycles.

This is directly affecting the important ecosystem services they provide to humans, a new report by the Convention on the Conservation of Migratory Species of Wild Animals (CMS), a UN biodiversity treaty stated.

The report published at the ongoing 28th Conference of Parties to the United Nations Framework Convention on Climate Change put forwards the direct impacts of climate change on aerial, aquatic and terrestrial migratory species. These include poleward range shifts of terrestrial animals, changes in timing of migration and increased probability of deaths and survival due to extreme weather conditions such as heatwaves, torrential rains among others.

It also highlighted the effects on breeding success, especially with temperatures sensitive animals such as penguin, turtles, etc and their survival. The report identified the role of various species in mitigating impacts of climate change and their contribution to increase resilience to climatic hazards.

For instance, whalesthat have long life span play crucial role in carbon capture. It is estimated that during their lifespan they store massive amounts of carbon in their body and lock the carbon as their carcasses reaches the bottom of the ocean after their death. As such, each whale has an estimated potential to sequester 0.062 megatonnes of carbon annually.

In other examples, mammals like bats help to maintain the biodiveristy through seed dispersal, saiga antelopes help improve resilience of grasslands by preventing wildfires and vultures help reduce disease transmission and risk of spread of zoonotic disease spillover to humans.

The report presented mounting evidence of how global rise in temperatures have affected the migratory species.

Warmer temperatures are affecting the timing and abundance of food availability such as plankton blooms, the authors noted. Cold-water copepods are replaced with warm-water species that emerge later in the year, reducing the flush of plankton for fish which results in shortage of juvenile fish such as sandeels in the vicinity of seabird colonies crucial for seabirds, they observed.

Little penguins forage longer distances during prolonged drought induced by El Nino and decrease breeding success, according to the report. Change in timings of peak spring abundance and oceanic currents also affected the seabirds, it added.

In addition, extreme weather affected Shag, which have poor weather-proofing and become extremely prone to high mortality due to stormy or wet conditions. The report found that rising sea levels also affect the birds as they are mainly cliff-nesters.

“For example, two migratory albatrosses (laysan and black-footed albatross) nesting in the Hawaiian Islands are predicted to lose 60 per cent of their nesting habitat with a 2-metre sea level rise,” the authors found.

Among waterbirds, the findings showed that extreme cold weather becomes fatal for wading bird population as observed among Greater Flamingos, Bitterns and coastal winter species such as Redshank found in the United Kingdom.

“It is worth noting that such extreme events can precipitate a decline from which the population cannot recover; for example, UK breeding populations of Northern Lapwing decreased as the result of a series of cold winters, and have not recovered due to insufficient reproductive capacity, despite the proximate cause of the decline no longer being present,” the researchers found.

With regards to raptors, the report revealed that higher temperatures resulted in decreased hunting frequency among birds and reduction in food consumption.

The higher temperatures were also found to affect Afro-Palearctic migratory passerines such as Barn Swallow chick growth causing reduction in their growth while drop in chick providing rates due to overheating among American migratory passerine, the Tree Swallow.

“High temperatures are linked to increased mortality in Great Reed Warblers, though their reproduction has been benefiting from improved rearing conditions,” the report found.

Moreover, the climate change tends to affect terrestrial mammals such as ungulates, herbivores and others as decline in rainfall resists in their food availability.

“Droughts have also been linked to increases in parasite loads in African Elephants and Lions, as more individuals rely on limited water resources and an increased prevalence of infectious diseases in Asian Elephants,” it found.

Increase in temperatures was found to have increased stress among terrestrial mammals, reduce reproductive success and decrease population sizes.

Report referred to the incident of over 300 African Elephants dying recently in Botswana as a result of biotoxins produced by cyanobacteria in drinking water, stimulated by extremes of hot and dry weather.

Habitat loss due to climate change was observed to be another factor that threatens populations such as Iranian leopard, lions, brown bears, gobi bears, Asian and African Elephants alike, the researchers noted.

They added that that increased temperatures and reduced ice extent directly impact krill populations, food for whales, and hunting areas for polar bears forcing them to take log migrations in search of food. The authors warned that polar bears may become entirely extinct by 2100.

“Seal and sea lion species that are reliant on sea ice for breeding may be particularly vulnerable to climate change. The Caspian and Grey Seals are the only CMS species that regularly breed on ice.”

The report further stated that sea ice declines may increase predation risk (Minke Whale declines have been partly linked to sea ice declines due to lack of shelter from predators). “Ice entrapments for Beluga Whales and Narwhals may increase due to increasing variability in sea ice,” it added.

With regards to reptiles, the researchers observed the ongoing changes that temperature sensitive turtles and crocodiles are undergoing. Temperature-dependent sex determination and increases in the female:male hatchling sex ratio, due to increasing temperatures.”

Among bony fish species, the change in temperature is affecting their spawning and altering fish metabolism and increasing in migration, the authors noted.

In a press statement, professor Colin Galbraith, former chair of Joint Nature Conservation Committee and CMS COP-appointed councillor for climate change, said, “This report sets out robust scientific evidence that climate change is already having a significant impact on many species around the world that are dependent on migration for their survival”.

He added that time is running out on the fate of many iconic species. “We owe it to them to raise global awareness that solutions are possible, and call on governments to use this report to take action, seeking out nature based solutions that will help migratory species and that can reduce the impacts of climate change,” he added.

Amy Fraenkel, executive secretary of CMS, said, “Climate change is severely disrupting these critical paths, altering ecosystems and affecting the availability of resources. This disruption serves as a crucial red flag, highlighting the broader implications of climate change not just for these species, but for the interconnected web of life on Earth. This report underscores the need for immediate and concerted global action to mitigate these impacts and protect the future of migratory species.”

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