Live Fast, Die Young: Experimental Evidence of Population Extinction Risk due to Climate Change

Abstract

Evidence has accumulated in recent decades on the drastic impact of climate change on biodiversity. Warming temperatures have induced changes in species physiology, phenology, and have decreased body size. Such modifications can impact population dynamics and could lead to changes in life cycle and demography. More specifically, conceptual frameworks predict that global warming will severely threaten tropical ectotherms while temperate ectotherms should resist or even benefit from higher temperatures. However, experimental studies measuring the impacts of future warming trends on temperate ectotherms' life cycle and population persistence are lacking. Here we investigate the impacts of future climates on a model vertebrate ectotherm species using a large-scale warming experiment. We manipulated climatic conditions in 18 seminatural populations over two years to obtain a present climate treatment and a warm climate treatment matching IPCC predictions for future climate. Warmer temperatures caused a faster body growth, an earlier reproductive onset, and an increased voltinism, leading to a highly accelerated life cycle but also to a decrease in adult survival. A matrix population model predicts that warm climate populations in our experiment should go extinct in around 20 y. Comparing our experimental climatic conditions to conditions encountered by populations across Europe, we suggest that warming climates should threaten a significant number of populations at the southern range of the distribution. Our findings stress the importance of experimental approaches on the entire life cycle to more accurately predict population and species persistence in future climates.

Fig 1. The Metatron.

A: Aerial view of the structure. On the right, top shutters are closed on 17 enclosures. Credits: Quentin Bénard. B: Close view of the structure. On the bottom left, an enclosure with open shutters. On the top right, an enclosure with closed shutters. C: Inside view of one enclosure. D: Entrance of the two half-corridors of one enclosure. E: Pole containing the sensors recording temperature, humidity, and illuminance inside of the enclosure as well as the sprinkler system, protected with plastic and labeled with the patch identification number. F: Pitfall trap at the end of one corridor. G: One of the two ponds set in each enclosure. H and I: Rock and logs allowing for lizard thermoregulation, set in each corner of the enclosures.

Fig 2

(a) Juvenile annual body growth (mean ± SE) depending on the temperature treatment. Body growth is calculated as the difference between snout–vent length at birth and snout–vent length at recapture after one year, measured in mm. (b) Female juvenile probability of gravidity at one year old (mean ± SE) depending on the temperature treatment. (c) Adult and yearling annual survival probability (mean ± Standard Error [SE]) depending on the temperature treatment. (d) Clutch size of females that laid a second clutch during the 2012 summer (mean ± SE) depending on the temperature treatment. Underlying data can be found in S7 Table.

Fig 3. Potential risk from climate change for common lizard populations across Europe inferred from current maximum temperatures experienced by these populations.

Colors represent “risk profiles” of the populations, from A: imminent risk (purple) to F: low risk (green), see S4 Text, S6 Table. Populations in risk levels from A to C (purple, red and dark orange) will be threatened by a 2°C increase in temperatures. Populations in risk level D (light orange) will be threatened by a 3°C temperature increase, and risk level E (yellow) will be threatened by a 4°C temperature increase.