Climate change and human pressure make migration difficult for animals, study finds


Washington: Animals that migrate north to breed are threatened by ongoing climate change and increasing human pressure, a study by an international research team has found.
These animals are losing prior advantages to migration, declining in numbers, and doing much worse than their resident counterparts, the study, published in the journal Trends in Ecology and Evolution, found.

Many mammals, birds and insects migrate long distances north to reproduce, taking advantage of abundant seasonal food, fewer pests and diseases, and relative safety from predators.

However, the international research team, including scientists from the University of Bath, have found that climate change and increasing human pressure have eroded these benefits and, in many cases, led to lower reproductive success. and higher mortality in migratory species.

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Researchers warn that the reduced benefits of long-distance migration have potentially serious consequences for the structure and function of ecosystems.

They highlighted 25 recent studies, describing how migration becomes less profitable for a variety of land animals, including caribou, shorebirds and monarch butterflies, which migrate over 1,000 km in summer to northern temperate regions. and arctic to breed and return south in winter.

Traveling such long distances is very expensive in terms of energy, but the benefits of the food supply, less disease and predators meant the benefits outweighed the cost. However, researchers say that is no longer the case for many populations.

While some animals might move their breeding grounds slightly further north to compensate for changing environmental conditions, migratory animals are programmed to continue the dangerous journey each year to breed, despite the lack of benefits.

Dr Vojtch Kubelka, lead author and former visiting scholar at the Milner Center for Evolution at the University of Bath, said:

These findings are alarming. We have lived with the idea that northern breeding grounds are safe havens for migrating animals. On the contrary, the many arctic and temperate sites in the north can now represent ecological traps or worse yet degraded environments for various migratory animals, including shorebirds, caribou and butterflies.

Food supplies and availability in the north may be climatically incompatible with breeding migratory animals, resulting in higher offspring mortality, as described for many migratory birds.

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In addition, new parasites and pathogens are appearing in the Arctic, creating new pressures, and top predators are increasingly preying on nests and eating eggs and chicks before they reach birth. chance to fly away.

Dr Kubelka said:

Lemmings and voles were the primary food source for predators such as arctic foxes, however, milder winters can cause rain to fall on snow and then freeze, preventing lemmings from reaching their food. With fewer lemmings and voles for food, foxes instead eat the eggs and chicks of migrating birds. We have seen that nest predation rates by migratory Arctic shorebirds have tripled over the past 70 years, largely due to climate change.

The authors suggest that the northern arctic and temperate breeding areas require special conservation attention, in addition to the well-known issues at staging and wintering grounds for migratory species.

Alongside concrete conservation measures, the authors provide a simple framework on how to map stressors for migrating animals across space and time, helping to distinguish between suitable, naturally improved, or protected habitats. on the one hand and ecological traps or degraded environments with or eroded benefits for migratory behavior on the other.

Dr Kubelka said:

The recognition of emerging threats and the proposed framework for classifying the profitability of migration will identify the populations and regions most at risk, allowing the implementation of appropriate conservation measures.

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Professor Tamas Szekely, holder of the Royal Society Wolfson Research Merit Award at the Milner Center for Evolution at the University of Bath, said:

The migration of animals from equatorial regions to northern temperate regions and the Arctic is one of the largest movements of biomass in the world. But with reduced profitability of migratory behavior and a smaller number of descendants joining the population, the negative trend will continue and fewer and fewer individuals will return to the North. These patterns are particularly threatening to migratory animals, as many of these species are already adversely affected outside the breeding season at their stopover and wintering grounds – and many previously relied on northern latitudes to provide relatively safe breeding grounds, ”Szekely added. .

Professor Rob Freckleton, School of Ecology and Evolutionary Biology at the University of Sheffield, said:

Our review highlights that there are possible threats to migratory species. More research is needed and our article points out that solutions are really difficult due to the vast areas involved.

(Except for the title, this story was not edited by NDTV staff and is posted from a syndicated feed.)

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