Are animals immune systems prepared for climate change?

The accelerated melting of polar ice, the upsurge in natural fires or the slowing of ocean currents, are among the most remarkable consequences of climate change. However, more "silent" consequences must also be considered. This has been demonstrated by Swedish researchers by showing that the immune systems of many animals, especially birds, depend on their preferred environment and the climate there. As a result, climate change could lead to the emergence of new diseases that animals' immune systems may not be able to manage.

Researchers have for the first time found a link between the immune systems of different bird species and the different climatic conditions in which they live. Researchers at Lund University in Sweden believe that, as the climate changes, some birds may be exposed to diseases that they are not equipped to manage.

The results of the study, published in the journal PRSB: Biological Sciences , indicate that evolution has calibrated the immune system of a number of bird species over millions of years, enabling them to cope with diseases specific to the particular environment and climate in which they live.

An immune system potentially vulnerable to climate change

Rapid climate change increases the risk that these tailor-made immune systems will be weak, not just in birds. Emily O'Connor, one of the study's biologists, thinks that the results could also apply to some other animals because the immune system genes they examined are common to all vertebrates .

“Evolution may not be able to 'keep up' with climate change. There is a risk that many animals will simply not be able to cope with changes in the number and type of pathogens to which they will be exposed,” she explains.

Number of complex histocompatible alleles (allelic diversity) as a function of precipitation (A) and temperature (C). The data show that the immune genome is directly dependent on the climate. Credits: Emily A. O'Connor et al. 2020

As the climate changes and, for example, northern Europe becomes warmer and wetter, diseases that did not previously exist in temperate climates may begin to appear. This can be a challenge for some animals.

Emily O'Connor and her colleagues studied 37 different bird species living in different climatic regions. They studied the diversity of genes in the immune system of each species, which influences their effectiveness in fighting disease.

An immune genome directly linked to the environment and its climate

They also looked at temperature and precipitation for different regions from 1901 to 2017. In this way, they demonstrated that the diversity of genes in a species' immune system is linked to the climate in which it lives.

Species that live their whole lives in tropical regions, areas rich in precipitation and which do not move, have the most varied immune system genes. This great diversity allows these species to resist more pathogens.

Number of complex histocompatible alleles (allelic diversity) according to the resident or migratory character (A) and the climate (B). Credits: Emily A. O'Connor et al. 2020

Migratory birds which spend their winters in tropical regions and breed in temperate climates have an immune system similar to that of resident European birds. According to the researchers, this could be due to the fact that they are able to escape the disease by moving around.

Bibliography: Wetter climates select for higher immune gene diversity in resident, but not migratory, songbirds Emily A. O'Connor, Dennis Hasselquist, Jan-Åke Nilsson, Helena Westerdahl and Charlie K. Cornwallis Published:29 January 2020 https://doi.org/10.1098/rspb.2019.2675