Climate change may lead to the collapse of the population of lizards that are common in the deserts of the Land of Israel
"The loss of biodiversity in our world is a serious phenomenon that is constantly worsening and expanding," says doctoral student Gavin Stark. "According to data from the International Union for Conservation of Nature (IUCN), animal populations in the world decreased by 69% on average between 1970 and 2018, and approximately 30% of mammal species, approximately 25% of bird and reptile species, and approximately 40% of amphibian species Life is now in danger of extinction. This phenomenon has two main factors: climate change, such as frequent heat waves and cold waves, and global warming in general, which makes it difficult for many species to survive, and the destruction of habitats by humans, for example by building cities, mining minerals, cutting down trees, etc.
Researchers at Tel Aviv University have developed a computational model that predicts changes in the behavior of animals according to the expected changes in the climate and habitats where they live. The study focused on the lizard called the desert lizard common in the deserts of the Land of Israel, and predicted future changes in its behavior following the expected significant increase in temperature (plus 6.5 degrees Celsius in the summer) by the end of this century. "Our findings are alarming", claim the researchers, "the model predicts, among other things, that these lizards will reduce their activity to a minimum in the hot summer, which could harm their nutrition and reproduction, and possibly even cause the population to collapse."
The research was led by Dr. Ophir Levy and PhD student Gavin Stark from the School of Zoology and the Steinhardt Museum of Nature at Tel Aviv University, and in collaboration with researchers at the Chinese Academy of Sciences in Beijing and Princeton University in the USA. The article was published in the journal Global Change Biology.
Between sun and shade
In the current study, the researchers sought to examine how climate change and the destruction of habitats increase the pressure on animals in their natural environment, and affect their behavior and their chances of survival. To this end, they chose to focus on a lizard called Desert Eyenonite that lives in the Judean Desert - an area where extreme living conditions already prevail today, pushing the animals to their limits. The species that live in this area, including the clouded lizard, have managed to adapt to the harsh conditions, such as a soil temperature of 70-60 degrees Celsius in the summer, by transferring most of their activity to shaded micro-habitats.
Dr. Ofir Levy explains: "Lizards are cold-blooded, so they need the environmental temperature to regulate their body heat. In the desert, they usually go out into the open to soak up the sun's rays, and alternatively hide in the shadow of rocks and bushes to cool down and balance their body temperature. This behavior is called thermoregulatory behavior. We wanted to examine if and in what way this behavior will change in the coming decades, when temperatures will rise due to global warming, and the conditions in the desert will become even more extreme."
The researchers collected lizards from the desert and brought them to the laboratory at the School of Zoology at Tel Aviv University. Here they exposed them to varied conditions and recorded their preferences and their thermoregulatory behavior under varying conditions. At the same time, they placed mobile meteorological stations in the desert that measured environmental data, with an emphasis on micro-habitats under rocks and bushes, where the lizard finds shade and shelter from the sun's rays.
Gavin Stark: "Unlike previous studies that referred only to a basic distinction between sun and shade, our study added new critical information: the type of shelter - bush or rock, and its size - large, medium or small. This is in light of the understanding that there is significance, for example, in the size of the rock that provides shade for the lizard: in a study we found that in the summer, during the hottest hours, the lizards prefer to hide under large rocks, and this can be explained by the relatively comfortable temperature they find there, because a large rock heats (and cools) more slowly . At the same time, the bushes have a variety of their own important benefits for the lizard: in addition to shade from the sun, they provide it with food, since they are a habitat for insects, and their roots create burrows that serve as shelter from predators and at night."
survive in cold blood
All the data collected in the laboratory and in the field, alongside international models predicting future temperatures, were fed into a biophysical computational model developed especially for the study, which applies physical equations to biological data. From this model, detailed predictions were obtained regarding the lizard's choices and behaviors under changing conditions, from today until the year 2100.
Gavin Stark explains: "According to our findings, the lizard's behavior is expected to change dramatically following the increase in temperature - an increase of 6.5 degrees Celsius on average in summer and 4.9 degrees on average in winter by the end of the 21st century. Today the lizards are active throughout the year, with adjustments to the different seasons, but in the future they are expected to significantly reduce their activity in the summer, when the temperatures will be too high even under large rocks, and the vegetation may be significantly reduced. In this season, they will stay mainly in the burrows, and will emerge from there only for a short time early in the morning to find food. In this situation there is a real danger that they will not be able to get enough food due to differences in the hours of activity between them and their prey (mainly ants and termites). The main activity of the lizards will therefore be transferred to the winter season, which will be warmer, but a change in their behavior is expected in this season as well. The model found that in winter they would prefer to stay in an open area to keep warm, and hide only for a short time under small rocks and bushes that provide a microclimate with a relatively high temperature, while the large rocks would be too cold for them. These changes in thermoregulatory behavior will greatly reduce the lizards' opportunities to find food and reproduce, and may even lead to the collapse of the population."
"These changes in thermoregulatory behavior will greatly reduce the lizards' opportunities to find food and reproduce, and may even lead to the collapse of the population."
Dr. Levy concludes: "In our research, we built a unique computational model that examines conditions in a variety of micro-habitats, compares them, and predicts changes in the behavior patterns of the lizard we tested following climate warming and the loss of habitats (mainly shrubs) until the end of the current century. We estimate that these changes in behavior may endanger the lizard's nutrition and reproduction, and cause significant damage to the local and national population. Using our model it is possible to examine which micro-habitats are important to preserve in order to prevent such damage, and also to identify habitats that are not important today but may become critical in the future, especially in areas with extreme conditions. It is important to note that the model can serve as a basis for developing additional models for other regions of the world, with a temperate or tropical climate for example, as well as for different types of animals, such as mammals, birds, amphibians and insects."
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