Rainforest regeneration rescues bat communities in aftermath of fragmentation

Rainforest loss is fuelling a tsunami of tropical species extinctions. However, not all is doom and gloom. A new study, conducted in the Brazilian Amazon, suggests that ecological cataclysms prompted by the fragmentation of the forest can be reverted by the regeneration of secondary forests, offering a beacon of hope for tropical forest biodiversity across the world.

Credit: Mark Moffett/ Minden Pictures/National Geographic Stock

The international team of researchers found that species strongly associated with primary forest were heavily depleted after 15 years of man-made disruption including the burning and clearing of forest stands,

However, 30 years down the line, and with the regeneration of secondary regrowth, many of the species that had abandoned the area had made a comeback.

"If you compare the time periods, it is apparent that taking a long-term view is paramount to uncovering the complexity of biodiversity in human-modified landscapes," said senior researcher Dr. Christoph Meyer, lecturer in global ecology and conservation at the University of Salford.

The study, published in Nature: Scientific Reports, measured the impacts of forest break-up of 50 species of bat (approx. 6,000 animals).

Bats comprise roughly one fifth of all mammal species and display wide variation in foraging behaviour and habitat use, making them an excellent model group for the research.

"The responses exhibited by bats offer important insights into the responses of other taxonomic groups." says Ricardo Rocha, lead author of the study from the University of Lisbon.

"The recovery that we have documented mirrors the patterns observed for beetle and bird communities within the Amazon.

"These parallel trends reinforce the idea that the benefits of forest regeneration are widespread, and suggest that habitat restoration can ameliorate some of the harm inflicted by humans on tropical wildlife", he adds.

The results of the current study contrast with the catastrophic faunal declines observed during a similar time window in rodent communities in the 'forest islands' of the Chiew Larn reservoir in Thailand.

"The recovery observed at the Amazon was mostly due to the recolonization of previously deforested areas and forest fragments by old-growth specialist bats. This recolonization is likely attributable to an increased diversity and abundance of food resources in areas now occupied by secondary forest, fulfilling the energetic requirements of a larger set of species", explains Rocha.

However, the short-term nature of most studies has substantially impaired the capacity of researchers to properly capture the intricate time-related complexities associated with the effects of forest fragmentation on wildlife.

Source: University of Salford [February 28, 2018]

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King penguins may be on the move very soon

More than 70 percent of the global King penguin population, currently forming colonies in Crozet, Kerguelen and Marion sub-Antarctic islands, may be nothing more than a memory in a matter of decades, as global warming will soon force the birds to move south, or disappear. This is the conclusion of a study published in the journal Nature Climate Change and performed by an international team of researchers.

More than 70 percent of the global King penguin population may be nothing more than a memory in a matter of decades,
 as global warming will soon force the birds to move south, or disappear [Credit: Robin Cristofari]

"The main issue is that there is only a handful of islands in the Southern Ocean and not all of them are suitable to sustain large breeding colonies" says Robin Cristofari, first author of the study, from the Institut Pluridisciplinaire Hubert Curien (IPHC/CNRS/University of Strasbourg) and the Centre Scientifique de Monaco (CSM).

King penguins are in fact picky animals: in order to form a colony where they can mate, lay eggs and rear chicks over a year, they need tolerable temperature all year round, no winter sea ice around the island, and smooth beach of sand or pebbles. But, above all, they need an abundant and reliable source of food close by to feed their chicks. For millennia, this seabird has relied on the Antarctic Polar Front, an upwelling front in the Southern Ocean concentrating enormous amounts of fish on a relatively small area.

Yet, due to climate change, this area is drifting south, away from the islands where most King penguins currently live. Parents are then forced to swim farther to find food, while their progeny is waiting, fasting longer and longer on the shore. This study predicts that, for most colonies, the length of the parents' trips to get food will soon exceed the resistance to starvation of their offspring, leading to massive King penguin crashes in population size, or, hopefully, relocation.

King penguins are picky animals [Credit: Celine LeBohec]

Using the information hidden away in the penguin's genome, the research team has reconstructed the changes in the worldwide King penguin population throughout the last 50,000 years, and discovered that past climatic changes, causing shifts in marine currents, sea-ice distribution and Antarctic Polar Front location, have always been linked to critical episodes for the King penguins. However, hope is not lost yet: King penguins have already survived such crises several times (the last time was 20 thousand years ago), and they may be particularly good at it.

"Extremely low values in indices of genetic differentiation told us that all colonies are connected by a continuous exchange of individuals," says Emiliano Trucchi formerly at the University of Vienna and now at the University of Ferrara, one of the coordinator of the study. "In other words, King penguins seem to be able to move around quite a lot to find the safest breeding locations when things turn grim."

But there is a major difference this time: for the first time in the history of penguins, human activities are leading to rapid and/or irreversible changes in the Earth system, and remote areas are no exception. In addition to the strongest impact of climate change in Polar Regions, Southern Ocean is now subject to industrial fishing, and penguins may soon have a very hard time fighting for their food.

Penguins form colonies in Crozet, Kerguelen and Marion sub-Antarctic islands [Credit: Celine LeBohec]

"There are still some islands further south where King penguins may retreat," notes Celine Le Bohec (IPHC/CNRS/University of Strasbourg and CSM), leader of the programme 137 of the French Polar Institut Paul-Emile Victor within which the study was initiated, "but the competition for breeding sites and for food will be harsh, especially with the other penguin species like the Chinstrap, Gentoo or Adelie penguins, even without the fisheries. It is difficult to predict the outcome, but there will surely be losses on the way. If we want to save anything, proactive and efficient conservation efforts but, above all, coordinated global action against global warming should start now."

Source: University of Vienna [February 26, 2018]

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In 16 years, Borneo lost more than 100,000 orangutans

Over a 16-year period, about half of the orangutans living on the island of Borneo were lost as a result of changes in land cover. That's according to estimates reported in Current Biology showing that more than 100,000 of the island's orangutans disappeared between 1999 and 2015.

A Bornean orangutan [Credit: Marc Ancrenaz]

Many of those losses were apparently driven by the demand for logging, oil palm, mining, paper, and associated deforestation. However, many orangutans have also disappeared from more intact, forested areas, the researchers say. Those findings suggest that hunting and other direct conflicts between orangutans and people remain a major threat to the species.

"The decline in population density was most severe in areas that were deforested or transformed for industrial agriculture, as orangutans struggle to live outside forest areas," says Maria Voigt of the Max Planck Institute for Evolutionary Anthropology in Germany. "Worryingly, however, the largest number of orangutans were lost from areas that remained forested during the study period. This implies a large role of killing."

To estimate changes in the size of the orangutan population over time, Voigt, along with Serge Wich from Liverpool John Moores University in the UK and their colleagues representing 38 international institutions, compiled field surveys conducted from 1999 to 2015. They extrapolated the overall size of the island's population from the number of orangutan nests observed throughout the species' range in Borneo.

This photograph shows where Bornean forest was cleared for road development 
[Credit: Marc Ancrenaz]

All told, the team observed 36,555 nests. They estimated a loss of 148,500 Bornean orangutans between 1999 and 2015.The data also suggest that only 38 of the 64 identified spatially separated groups of orangutans (known as metapopulations) now include more than 100 individuals, which is the accepted lower limit to be considered viable.

In order to identify the likely causes of those losses, the researchers relied on maps of estimated land-cover change over the same period that have been made possible by advances in remote sensing technology. The comparison of orangutan and habitat losses suggests that land clearance caused the most dramatic rates of decline. However, a much larger number of orangutans were lost in selectively logged and primary forests. That's because while the rates of decline were less precipitous in those areas, that's also where far more orangutans are found, the researchers explain.

By 2015, they report, about half of the orangutans estimated to live on Borneo in 1999 were found in areas in which resource use has since caused significant changes to the environment. Based on predicted future losses of forest cover and the assumption that orangutans ultimately cannot survive outside forest areas, the researchers predict that over 45,000 more orangutans will be lost over the next 35 years.

This photograph shows where Bornean forest was cleared for a factory 
[Credit: Marc Ancrenaz]

They say that effective partnerships with logging companies and other industries are now essential to the Bornean orangutan's survival. Public education and awareness will also be key.

"Orangutans are flexible and can survive to some extent in a mosaic of forests, plantations, and logged forest, but only when they are not killed," Wich says. "So, in addition to protection of forests, we need to focus on addressing the underlying causes of orangutan killing. The latter requires public awareness and education, more effective law enforcement, and also more studies as to why people kill orangutans in the first place."

They note that Indonesia and Malaysia are both currently developing long-term action plans for orangutan conservation. By taking into account past failures, the hope is that new strategies to protect orangutans can be developed and implemented.

Source: Cell Press [February 15, 2018]

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Research identifies 'evolutionary rescue' areas for animals threatened by climate change

As winters arrive later and snow melts earlier, the worldwide decrease in snow cover already may have dramatic impacts on animals that change coat colors with the seasons. An international scientific team led by University of Montana Professor L. Scott Mills has set out to discover whether adaptive evolution can rescue these animals in the face of rapidly changing climate.

Brown and white snowshoe hares on snow at a University of Montana research facility
[Credit: L.S. Mills research photos by Jaco and Lindsey Barnard]

Twenty-one species of mammals and birds rely on the ability to change their coat color from brown in summer to white in winter to avoid fatal encounters with predators, but in some parts of their range individuals forgo the white molt and remain brown in winter.

"Weasels in the southern U.S. and mountain hares in Ireland, for example, have evolved to remain brown year-round," Mills said. "This is a genetic adaptation to retain camouflage in areas where snow is intermittent or sparse."

Mills' group previously found that winter white snowshoe hares confronting snowless ground have higher mortality rates that could drive massive population declines as snow duration continues to decrease. Other scientists have pointed to coat-color mismatch against snowless ground as a cause for recent range decreases of hares, ptarmigan and other species.

Brown and white snowshoe hares on bare ground at a University of Montana research facility
[Credit: L.S. Mills research photos by Jaco and Lindsey Barnard]

In a new article in Science, Mills' team identified areas that could foster rapid "evolutionary rescue" of these species particularly vulnerable to climate change. The study describes how the international team mapped "polymorphic zones" for eight color-changing species, including hares, weasels and the Arctic fox. In these zones, both brown and white individuals coexist in winter.

"These areas hold the special sauce for rapid evolutionary rescue," Mills said. "Because they contain winter-brown individuals better adapted to shorter winters, these polymorphic populations are primed to promote rapid evolution toward being winter brown instead of white as climate changes."

The authors emphasize that these hotspots for evolutionary rescue are not magic fortresses that will prevent climate change effects on wild animals.

"Ultimately, the world must reduce carbon dioxide emissions or else the climate effects will overwhelm the ability of many species to adapt," co-author Eugenia Bragina said. "But by mapping these adaptive hotspots, we identify places where people could help foster evolutionary rescue in the short term by working to maintain large and connected wildlife populations."

Source: The University of Montana [February 15, 2018]

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When it comes to extinction, body size matters

On a certain level, extinction is all about energy. Animals move over their surroundings like pacmen, chomping up resources to fuel their survival. If they gain a certain energy threshold, they reproduce, essentially earning an extra life. If they encounter too many empty patches, they starve, and by the end of the level it's game over.

In classic extinction models, animals move over their surroundings like pacmen, chomping up resources
to fuel their survival [Credit: Laura Chambliss/Studio Yopp]

Models for extinction risk are necessarily simple. Most reduce complex ecological systems to a linear relationship between resource density and population growth -- something that can be broadly applied to infer how much resource loss a species can survive.

This week in Nature Communications, an interdisciplinary team of scientists proposes a more nuanced model for extinction that also shows why animal species tend to evolve toward larger body sizes. The Nutritional State-structured Model (NSM) by ecologist Justin Yeakel (UC Merced), biologist Chris Kempes (Santa Fe Institute), and physicist Sidney Redner (Santa Fe Institute) incorporates body size and metabolic scaling into an extinction model where 'hungry' or 'full' animals, great and small, interact and procreate on a landscape with limited resources.

"Unlike many previous forager models, this one accounts for body size and metabolic scaling," Kempes explains. "It allows for predictions about extinction risk, and also gives us a systematic way of assessing how far populations are from their most stable states."

In the NSM, hungry animals are susceptible to mortality, and only full animals have the capacity to reproduce. Because animals' energetic needs change with body size, the researchers based their calculations for replenishment and reproduction on biological scaling laws that relate body size to metabolism.

They found that species of different sizes gravitate toward population states most stable against extinction. The states they derived in the model reproduce two oft-observed patterns in biology. The first, Damuth's law, is an inverse relationship between body size and population density: the bigger the species, the fewer of individuals cohabitate in a given area. Within the NSM, this fewer/larger more/smaller pattern emerges because large species are most stable against starvation in small numbers, while small species can afford to reach larger population densities.

The second relationship, Cope's rule, holds that terrestrial mammals tend to evolve toward larger body sizes. This NSM shows that, overall, larger animals with slower metabolisms are the most stable against extinction by starvation. It even predicts an energetically "ideal" mammal, robust in the face of starvation, which would be 2.5 times the size of an African elephant.

"As we incorporated more realism into how quickly organisms gain or lose body fat as they find or don't find resources, the results of our model began aligning with large-scale ecological and evolutionary relationships. Most surprising was the observation that the NSM accurately predicts the maximum mammalian body size observed in the fossil record," explains Yeakel. Though the model doesn't account for predation, it does offer a dynamic and systematic framework for understanding how foragers survive on limited resources.

"The dynamics of foraging and the interaction of body size in foraging and resource availability, these are all rich problems for which there is beautiful phenomenology," says Redner. "I hope some of this will have relevance in managing resources and ensuring species don't go extinct."

Source: Santa Fe Institute [February 13, 2018]

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