Lake La Yeguada.
Photo Credit: Dunia Urrego
Scientific Frontline: "At a Glance" Summary: Ecosystem Rewilding in Panama
- Main Discovery: The prehistoric extinction of large herbivorous megafauna in Panama resulted in cascading ecological disruptions, specifically an increase in regional wildfires and a significant decline in plant species reliant on massive animals for seed dispersal.
- Methodology: Researchers analyzed 17,000-year-old sediment cores extracted from Lake La Yeguada. The team tracked historical herbivore populations using fungal spores originating from prehistoric dung, identified plant life via fossilized pollen, and measured historical wildfire frequency through charcoal deposits.
- Key Data: The sediment record revealed three distinct periods of megafauna population collapse occurring 13,600, 10,000, and 8,400 years ago. These declines were followed by subsequent ecosystem recoveries logged at 11,200, 9,000, and 7,600 years ago.
- Significance: The absence of large herbivores removes critical ecological functions, such as the consumption and trampling of understory vegetation that suppresses fire fuel. This establishes that contemporary megafauna loss poses severe, ongoing risks to current forest biodiversity.
- Future Application: Paleoecological records will serve as baseline metrics for targeted trophic rewilding initiatives, guiding the careful selection and introduction of ecologically equivalent herbivore species to restore lost ecosystem functions in Central American forests.
- Branch of Science: Paleoecology, Conservation Biology, and Geosciences.
- Additional Detail: The original declines of these prehistoric herbivores, which included giant ground sloths and elephant-like Cuvieronius, strongly correlate with early human arrival and subsequent environmental disturbance in the region.
Introducing large herbivores in Panama's forests could fill the gap left by extinct species, new research suggestions.
University of Exeter scientists studied lake sediments that contain traces of animals and plants dating back 17,000 years.
Many large herbivores that once roamed modern-day Panama have declined or died out – including the six-metre-long giant ground sloth and elephant-related creatures called Cuvieronius.
The new study reveals three major declines of plant-eating “megafauna” (animals over 45kg): 13,600, 10,000 and 8,400 years ago.
Large herbivores have greater impacts on ecosystems, and the study found forests and grasslands changed markedly when megafauna declined.
The team say their findings can provide a “baseline” for future rewilding to restore the ecological functions lost with the extinction of prehistoric megafauna.
“Just like elephants today, we found that large herbivores had a significant impact on ecosystems during the period we studied,” said lead author Felix Pym, from the University of Exeter.
“For example, there were fewer wildfires when large herbivores thrived – possibly because they ate and trampled on vegetation that can fuel fires.
“Also, when megafauna declined, so did plants with large fleshy fruits and seeds that are typically spread by large animals.
“It's visible from our record that the loss of megafauna had cascading impacts on ecosystem processes.”
The findings suggest that future declines of today's large herbivores could have profound consequences for biodiversity.
Conversely, “rewilding” by introducing new species or increasing populations of existing ones could restore nature – and its benefits to humans.
“As a large proportion of megafauna species that lived during the study period are now globally extinct or have underground severe declines, some rewilding efforts in Europe and North America have used the nearest equivalents and/or moved species from elsewhere in the world,” Pym said.
“Our study tells us something about what has been lost, and highlights a possible solution, but the selection of species for rewilding would require careful research and planning.”
Prehistoric poo
Explaining how the study worked, Pym said: “Large herbivores consume fungal spores from their environment, which are then excreted and grow into fungi in their dung.
“New fungal spores are dispersed, travel into lakes, and are then preserved in layers of sediment.
“The sediment also contains fossilized pollen, which allows us to identify plant species, and charcoal, which tells us when fires occurred.
“We took samples from sediments recovered from Lake La Yeguada and analyzed them for fungal spores, pollen and charcoal – revealing lots of information about past animals, plants and wider ecosystems.”
Fungal spores only reveal that large herbivores were present – not yet specific species – but existing bone evidence shows species that lived in the region during the period.
The causes of megafauna decline are also debated, but the arrival and disturbance of humans in Central America are likely factors.
After the periods of megafauna decline discovered by the study, recoveries take place at 11,200, 9,000 and 7,600 years ago – probably due to changes in the communities of large herbivores in the region. Professor Stephen Sitch, from Exeter's Global Systems Institute, said: “This study uses a novel approach to give us a holistic understanding of the tropical environment through time, including interactions between animals, fire, vegetation and climate.
“Exploring the past can help us understand today's tropical ecosystems, aid their conservation and together with rewilding approaches, help to restore lost ecosystem functions that we all benefit from.”
Funding: Natural Environment Research Council through its GW4+ Doctoral Training Partnership program.
Published in journal: Quaternary Science Reviews
Authors: Felix Pym, Felipe Franco-Gaviria, Marco Raczka, Gbotemi A. Adediran, Stephen Sitch, and Dunia H. Urrego
Source/Credit: University of Exeter | Russell Parton
Reference Number: es030326_01