Dozens of species of frogs, salamanders and other amphibians quietly disappeared from parts of Latin America in the 1980s and 2000s, with little notice from humans, outside of a small group of ecologists. Yet the amphibian decline had direct health consequences for people, according to a study from the University of California, Davis.
The study, published in the journal , links an amphibian die-off in Costa Rica and Panama with a spike in malaria cases in the region. At the spike鈥檚 peak, up to 1 person per 1,000 annually contracted malaria that normally would not have had the amphibian die-off not occurred, the study found.
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鈥淪table ecosystems underpin all sorts of aspects of human well-being, including regulating processes important for disease prevention and health,鈥 said lead author , a professor in the 澳门六合彩开奖结果走势图 Department of Environmental Science and Policy. 鈥淚f we allow massive ecosystem disruptions to happen, it can substantially impact human health in ways that are difficult to predict ahead of time and hard to control once they鈥檙e underway.鈥
![Chart with vertical axis showing malaria cases and horizontal axis the years 1980 to 2010s and blue and gold lines representing Panama and Costa Rica](/sites/default/files/media/images/Malaria-amphib%20spike%20chart_UC%20Davis.png)
A natural experiment
From the early 1980s to the mid-1990s, a deadly fungal pathogen called Batrachochytrium dendrobatidis, or 鈥淏d,鈥 traveled across Costa Rica, devastating amphibian populations. This amphibian chytrid fungus continued its path eastward across Panama through the 2000s. Globally, the pathogen led to the extinction of at least 90 amphibian species, and to the decline of at least 500 additional species.
Shortly after the mass die-off of amphibians in Costa Rica and Panama, both countries experienced a spike in malaria cases.
![beige, microscopic view of frog skin infected with Bd pathogen](/sites/default/files/media/images/BD%20frog%20skin%20microscope.jpg)
![yellow frog sits on beige surface with black background](/sites/default/files/media/images/Chiriqui%20Harlequin%20frog.jpeg)
Some frogs, salamanders and other amphibians eat hundreds of mosquito eggs each day. Mosquitoes are a vector for malaria. Scientists wondered, could the crash in amphibians have influenced the rise in malaria cases?
To find out, the researchers combined their knowledge of amphibian ecology, newly digitized public health record data, and data analysis methods developed by economists to leverage this natural experiment.
鈥淲e鈥檝e known for a while that complex interactions exist between ecosystems and human health, but measuring these interactions is still incredibly hard,鈥 said co-author Joakim Weill, a Ph.D. candidate at 澳门六合彩开奖结果走势图 when the study was conducted. 鈥淲e got there by merging tools and data that don鈥檛 usually go together. I didn鈥檛 know what herpetologists studied before collaborating with one!鈥
The results show a clear connection between the time and location of the spread of the fungal pathogen and the time and location of increases in malaria cases. The scientists note that while they cannot fully rule out another confounding factor, they found no evidence of other variables that could both drive malaria and follow the same pattern of die-offs.
![Purple, green and yellow map of Panama and Costa Rica representing malaria cases and amphibian die-offs](/sites/default/files/media/images/Malaria-amphibian%20dieoff%20map%20CR%20Pan_UC%20Davis.png)
Tree cover loss was also associated with an increase in malaria cases, but not nearly to the same extent as the loss of amphibians. Typical levels of tree canopy loss increase annual malaria cases by up to 0.12 cases per 1,000 people, compared to 1 in 1,000 for the amphibian die-off.
Trade threats
Researchers were motivated to conduct the study by concerns about the future spread of similar diseases through international wildlife trade. For instance, Batrachochytrieum salamandrivorans, or 鈥淏sal,鈥 similarly threatens to invade ecosystems through global trade markets.
Springborn said measures that could help prevent the spread of pathogens to wildlife include updating trade regulations to better target species that host such diseases, as our knowledge of threats evolve.
鈥淭he costs of putting those protective measures in place are immediate and evident, but the long-term benefits of avoiding ecosystem disruptions like this one are harder to assess but potentially massive, as this paper shows,鈥 Springborn said.
Additional co-authors include Karen Lips of University of Maryland, Roberto Ib谩帽ez of Smithsonian Tropical Research Institute in Panam谩, and Aniruddha Ghosh of 澳门六合彩开奖结果走势图 and the Alliance of Biodiversity International and CIAT in Kenya.
The study was funded by the National Science Foundation and the 澳门六合彩开奖结果走势图 Institute of the Environment.
Media Resources
Media Contacts:
- Michael Springborn, 澳门六合彩开奖结果走势图 Environmental Science and Policy, mspringborn@ucdavis.edu
- Kat Kerlin, 澳门六合彩开奖结果走势图 News and Media Relations, kekerlin@ucdavis.edu, 530-750-9195