Climate change and human pressure mean that migration may be "no longer worth it"

Many animals, including mammals, birds and insects, migrate long distances to the north to breed, use seasonal abundant food, fewer parasites and diseases, and are relatively safe carnivores
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However, an international research team including scientists from the University of Bath found that climate change and increasing human stress have eroded these benefits, in many cases leading to reduced reproduction success rates and higher mortality rates for migrating species
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Researchers warn that the reduced advantages of long-distance migration may have serious consequences for the structure and function of the ecosystem
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They highlighted 25 recent studies that describe how migration has become increasingly unprofitable for various land animals, including reindeer, waterfowl, and monarch butterflies
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From an energy point of view, long-distance travel is very expensive, but the benefits of food supply, fewer diseases and predators mean the benefits outweigh the costs.
However, the researchers say this is no longer the case for many populations
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Although some animals may shift their breeding range slightly to the north to compensate for changes in environmental conditions, migratory animals continue a dangerous journey to reproduce every year, although there is no benefit
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Vojtch Kubelka, the lead author of the study and a former visiting researcher at the Milner Center for Evolution at the University of Bath, said: "These findings are worrying
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"In contrast, many Arctic and northern temperate regions may now be ecological traps, or even worse environments for various migrating animals, including shorebirds, reindeer or butterflies
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The food supply and availability in North Korea may not be climatically compatible with the reproduction of migratory animals, leading to higher offspring mortality, as many migratory birds describe
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In addition, new parasites and pathogens are emerging in the Arctic, creating new pressures, with more and more top predators preying on nests, eggs, and chicks before they have a chance to be full-fledged
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"Lemmings and voles were once the main food sources for predators such as Arctic foxes.
However, warm winters can cause rain to fall on the snow and then freeze again, preventing the lemmings from getting food
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As there are fewer lemmings and voles that can be eaten, the fox turns to eat the eggs and chicks of migratory birds
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"We have seen that in the past 70 years, the nest predation rate of Arctic migratory birds has tripled.
This is largely due to climate change
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The author believes that, in addition to the well-known problems in migratory bird crossings and wintering areas, the Arctic and northern temperate breeding grounds need a lot of protection
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In addition to specific protection measures, the author also proposed a simple framework for mapping the stressors of animals migrating across time and space, helping to distinguish suitable habitats that are naturally improved or protected on the one hand, and ecological traps on the other.
Or a degraded environment reduces or erodes the benefits of migration
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Dr.
Kubelka said: “Awareness of emerging threats and the proposed classification framework for immigration benefits will help identify the most endangered populations and areas so that appropriate protection measures can be implemented
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Professor Tamás Székely, winner of the Royal Society Wolfson Research Achievement Award at the Milner Evolution Center, University of Bath, said: “The migration of animals from the equatorial region to the northern temperate zone and the Arctic is one of the largest movements of biomass in the world
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"The earth is a complex ecosystem-changes in the profitability of migration will affect the number of migratory animals, which will lead to changes in the composition of the species, the nutrient food web, and the function of the entire ecosystem
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"These patterns pose a particularly serious threat to migratory animals, because outside the breeding season, a large number of species have been negatively affected in their stopovers and wintering grounds, and many species previously relied on northern latitudes to provide relatively safe breeding grounds
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Professor Rob Freckleton from the School of Ecology and Evolutionary Biology at the University of Sheffield said: “Our review highlights the threats that migratory species may face
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Journal Reference :

1. Vojtěch Kubelka, Brett K.