Siesta in the shade during the hot parts of the day. The image conjures thoughts that are lazy and pleasant. Not so much for the global lizard population. For them it means death.
A new study, published in Science, predicts that almost 40% of all global lizard populations will be extinct by 2080. Why? Global warming.
Sinervo and his team of researchers from the University of California have build an elegant, simple computer model based mainly on the body temperature lizards need to be active and the temperature of the environment. The model calculates the risk of extinction for over 1200 lizard species around the globe.
Lizards are, just like all reptiles, cold blooded. This means they cannot regulate their own temperature like we can. They rely on the temperature of the environment to warm them up or cool them down, either by basking in the sun for a while or search for shelter. Their body can tolerate a certain range of temperatures in which it can be active. If their body is too cold they are inactive and if it gets too hot they suffer from heat stress and water loss like we do, eventually dying.
Heating it up
The problem arises with rising temperatures due to global warming and is simple: when it gets warmer lizards will spend more time in shelters and less time hunting and foraging. This results in too little energy to survive.
Spring temperatures seem pivotal as they interfere with breeding season. The study found that in areas where spring temperatures forced the lizards to shelter only about 4 hours a day they survived. When spring temperatures were forcing the lizards to seek cover for most of the day, they went (or already were) extinct.
‘That much downtime means the lizards will pretty much be starving to death and not laying eggs’ said Sinervo in an interview with National Geographic.
Future Predictions
His team put this information, combined with climate data back to 1975 and global warming predictions, into the computer model and calculated the amount of hours lizards would be incapacitated due to heat as well as the hottest temperatures for different parts of the world in the past, present and future.
The results accurately predict various extinctions that have already happened in different parts of the world. It also predicted in a disturbing 39% extinction of global lizard populations and a 20% extinction of all lizard species by 2080.
Areas that seem especially vulnerable are Madagascar and the Amazon. The Madagascan chameleon, Furcifer pardalis, that is shown on this blogs header is one of the reptiles at risk.
Another group at high risk is the live-bearing lizards: the lizards that bear live young instead of laying eggs. Their ecology forced them to develop somewhat lower body temperatures as high temperature might harm the offspring.
Extra Considerations
Although these results are strong and extremely disturbing, some scepticism is necessary. Evidence of local extinction is notoriously hard to find as you might just as well misinterpret a shrunken population that you haven’t detected as being extinct. Time will tell whether this study interpreted right.
Also, populations might move, finding cooler habitat where they aren’t as constricted in foraging time. This trait wasn’t included in the research. But it is worth a short comment.
As easy as it might sound to just move into a cooler habitat there is a catch. Cooler climate is found when moving away from the equator towards the poles or moving up a mountain. But what about the species that already live in those areas? Competition between new arrivals for space and for food might put even more stress on the population that was native to the colder climate and already had a problem with finding an even cooler climate. Moving might be the solution for one species, it might also be the sped-up death of others.
Header photo by Jean-Louis Vandevivère
A new study, published in Science, predicts that almost 40% of all global lizard populations will be extinct by 2080. Why? Global warming.
Sinervo and his team of researchers from the University of California have build an elegant, simple computer model based mainly on the body temperature lizards need to be active and the temperature of the environment. The model calculates the risk of extinction for over 1200 lizard species around the globe.
Lizards are, just like all reptiles, cold blooded. This means they cannot regulate their own temperature like we can. They rely on the temperature of the environment to warm them up or cool them down, either by basking in the sun for a while or search for shelter. Their body can tolerate a certain range of temperatures in which it can be active. If their body is too cold they are inactive and if it gets too hot they suffer from heat stress and water loss like we do, eventually dying.
Heating it up
The problem arises with rising temperatures due to global warming and is simple: when it gets warmer lizards will spend more time in shelters and less time hunting and foraging. This results in too little energy to survive.
Spring temperatures seem pivotal as they interfere with breeding season. The study found that in areas where spring temperatures forced the lizards to shelter only about 4 hours a day they survived. When spring temperatures were forcing the lizards to seek cover for most of the day, they went (or already were) extinct.
‘That much downtime means the lizards will pretty much be starving to death and not laying eggs’ said Sinervo in an interview with National Geographic.
Future Predictions
His team put this information, combined with climate data back to 1975 and global warming predictions, into the computer model and calculated the amount of hours lizards would be incapacitated due to heat as well as the hottest temperatures for different parts of the world in the past, present and future.
The results accurately predict various extinctions that have already happened in different parts of the world. It also predicted in a disturbing 39% extinction of global lizard populations and a 20% extinction of all lizard species by 2080.
Areas that seem especially vulnerable are Madagascar and the Amazon. The Madagascan chameleon, Furcifer pardalis, that is shown on this blogs header is one of the reptiles at risk.
Another group at high risk is the live-bearing lizards: the lizards that bear live young instead of laying eggs. Their ecology forced them to develop somewhat lower body temperatures as high temperature might harm the offspring.
Extra Considerations
Although these results are strong and extremely disturbing, some scepticism is necessary. Evidence of local extinction is notoriously hard to find as you might just as well misinterpret a shrunken population that you haven’t detected as being extinct. Time will tell whether this study interpreted right.
Also, populations might move, finding cooler habitat where they aren’t as constricted in foraging time. This trait wasn’t included in the research. But it is worth a short comment.
As easy as it might sound to just move into a cooler habitat there is a catch. Cooler climate is found when moving away from the equator towards the poles or moving up a mountain. But what about the species that already live in those areas? Competition between new arrivals for space and for food might put even more stress on the population that was native to the colder climate and already had a problem with finding an even cooler climate. Moving might be the solution for one species, it might also be the sped-up death of others.
Header photo by Jean-Louis Vandevivère
No comments:
Post a Comment