Lemurs are the world’s most endangered mammals, but planting trees can help save them



Black-and-white ruffed lemurs are important indicators of rainforest health.
Franck Rabenahy, CC BY-ND

Andrea L. Baden, Hunter College

Madagascar, the world’s fourth-largest island, is a global biodiversity hotspot.
Andrea Baden

The island of Madagascar off the southeastern coast of Africa hosts at least 12,000 plant species and 700 vertebrate species, 80% to 90% of which are found nowhere else on Earth.

Isolated for the last 88 million years and covering an area approximately the size of the northeastern United States, Madagascar is one of the world’s hottest biodiversity hotspots. Its island-wide species diversity is striking, but its tropical forest biodiversity is truly exceptional.

Sadly, human activities are ravaging tropical forests worldwide. Habitat fragmentation, over-harvesting of wood and other forest products, over-hunting, invasive species, pollution and climate change are depleting many of these forests’ native species.

Among these threats, climate change receives special attention because of its global reach. But in my research, I have found that in Madagascar it is not the dominant reason for species decline, although of course it’s an important long-term factor.

As a primatologist and lemur specialist, I study how human pressures affect Madagascar’s highly diverse and endemic signature species. In two recent studies, colleagues and I have found that in particular, the ruffed lemur – an important seed disperser and indicator of rainforest health – is being disproportionately impacted by human activities. Importantly, habitat loss is driving ruffed lemurs’ distributions and genetic health. These findings will be key to helping save them.

Deforestation from slash-and-burn agriculture in the peripheral zones of Ranomafana National Park, Madagascar.
Nina Beeby/Ranomafana Ruffed Lemur Project, CC BY-ND

The forest is disappearing

Madagascar has lost nearly half (44%) of its forests within the last 60 years, largely due to slash-and-burn agriculture – known locally as “tavy” – and charcoal production. Habitat loss and fragmentation runs throughout Madagascar’s history, and the rates of change are staggering.

This destruction threatens Madagascar’s biodiversity and its human population. Nearly 50% of the country’s remaining forest is now located within 300 feet (100 meters) of an unforested area. Deforestation, illegal hunting and collection for the pet trade are pushing many species toward the brink of extinction.

In fact, the International Union for Conservation of Nature estimates that 95% of Madagascar’s lemurs are now threatened, making them the world’s most endangered mammals. Pressure on Madagascar’s biodiversity has significantly increased over the last decade.

A red ruffed lemur, one of two Varecia species endemic to Madagascar.
Varecia Garbutt, CC BY-ND

Deforestation threatens ruffed lemur survival

In a newly published study, climate scientist Toni Lyn Morelli, species distribution expert Adam Smith and I worked with 19 other researchers to study how deforestation and climate change will affect two critically endangered ruffed lemur species over the next century. Using combinations of different deforestation and climate change scenarios, we estimate that suitable rainforest habitat could be reduced by as much as 93%.

If left unchecked, deforestation alone could effectively eliminate ruffed lemurs’ entire eastern rainforest habitat and with it, the animals themselves. In sum, for these lemurs the effects of forest loss will outpace climate change.

But we also found that if current protected areas lose no more forest, climate change and deforestation outside of parks will reduce suitable habitat by only 62%. This means that maintaining and enhancing the integrity of protected areas will be essential for saving Madagascar’s rainforest habitats.

Warm colors indicate areas where lemurs can move about readily, which promotes genetic diversity; cool colors indicate areas where they are more constrained and less able to mate with members of other population groups.
Baden et al. (2019), Nature Scientific Reports, CC BY-ND

In a study published in November 2019, my colleagues and I showed that ruffed lemurs depend on habitat cover to survive. We investigated natural and human-caused impediments that prevent the lemurs from spreading across their range, and tracked the movement of their genes as they ranged between habitats and reproduced. This movement, known as gene flow, is important for maintaining genetic variability within populations, allowing lemurs to adapt to their ever-changing environments.

Based on this analysis, we parsed out which landscape variables – including rivers, elevation, roads, habitat quality and human population density – best explained gene flow in ruffed lemurs. We found that human activity was the best predictor of ruffed lemurs’ population structure and gene flow. Deforestation alongside human communities was the most significant barrier.

Taken together, these and other lines of evidence show that deforestation poses an imminent threat to conservation on Madagascar. Based on our projections, habitat loss is a more immediate threat to lemurs than climate change, at least in the immediate future.

In 1961 naturalist David Attenborough filmed ruffed lemurs for the BBC.

This matters not only for lemurs, but also for other plants and animals in the areas where lemurs are found. The same is true at the global level: More than one-third (about 36.5%) of Earth’s plant species are exceedingly rare and disproportionately affected by human use of land. Regions where the most rare species live are experiencing higher levels of human impact.

Crisis can drive conservation

Scientists have warned that the fate of Madagascar’s rich natural heritage hangs in the balance. Results from our work suggest that strengthening protected areas and reforestation efforts will help to mitigate this devastation while environmentalists work toward long-term solutions for curbing the runaway greenhouse gas emissions that drive climate change.

A young woman participates in reforestation efforts in Kianjavato, Madagascar.
Brittani Robertson/Madagascar Biodiversity Partnership, CC BY-ND

Already, nonprofits are working hard toward these goals. A partnership between Dr. Edward E. Louis Jr., founder of Madagascar Biodiversity Partnership and director of Conservation Genetics at Omaha’s Henry Doorly Zoo, and the Arbor Day Foundation’s Plant Madagascar project has replanted nearly 3 million trees throughout Kianjavato, one region identified by our study. Members of Centre ValBio’s reforestation team – a nonprofit based just outside of Ranomafana National Park that facilitates our ruffed lemur research – are following suit.

At an international conference in Nairobi earlier this year, Madagascar’s president, Andry Rajoelina, promised to reforest 40,000 hectares (99,000 acres) every year for the next five years – the equivalent of 75,000 football fields. This commitment, while encouraging, unfortunately lacks a coherent implementation plan.

Our projections highlight areas of habitat persistence, as well as areas where ruffed lemurs could experience near-complete habitat loss or genetic isolation in the not-so-distant future. Lemurs are an effective indicator of total non-primate community richness in Madagascar, which is another way of saying that protecting lemurs will protect biodiversity. Our results can help pinpoint where to start.

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Andrea L. Baden, Assistant Professor of Anthropology, Hunter College

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The endangered species list: counting lemurs in Madagascar


File 20180723 189335 1t5uopy.jpg?ixlib=rb 1.1
The endangered Coquerel’s Sifaka lemur.
Shutterstock/Monika Hrdinova

Ian Colquhoun, Western University

Most people are familiar with the endangered species list. Officially known as the IUCN Red List of threatened species, it’s coordinated by the International Union for the Conservation of Nature (IUCN) and provides the most up-to-date indication of the health of the world’s plants, animals and fungi to guide critical conservation action.

Examples include reports on declining leopard populations and improving mountain gorilla numbers. The list also signals when a species hasn’t been sighted in decades, is feared extinct, or has been “rediscovered” – as was the case for the large-billed reed-warbler.

To date, more than 91 000 species have been assessed for The IUCN red list. But, how is the list constructed and who is involved?

It’s a surprisingly complex process, involving the combined efforts of literally thousands of researchers. These “specialist group” volunteers use their expertise and time to create and maintain a central database which monitors the conservation statuses of the planet’s species. For mammals alone, there are 37 specialist groups.

My own involvement in contributing to the list has been through the Madagascar section of the IUCN Primate Specialist Group. This group involves approximately 450 primatologists worldwide. We are organised into specialist sections according to the biological classification of primate groups, such as the great apes, or regional areas of primate occurrence like South America or Africa. The Madagascar section of the group includes about 90 researchers who specialise in the study of lemur species.

Cyclical evaluation

Every five years the various specialist groups undertake reevaluations of the conservation statuses of the species on which they focus. This is currently being carried out for all 113 known lemur species by our section.

The last conservation assessment, conducted back in 2012, led to the alarming conclusion that lemurs are the most endangered group of mammals on the planet – 94% of all lemur species were classified as either “endangered” or “critically endangered”. A lot can change in five years. Since then, new lemur species have been described and there’s been a wealth of new field study data gathered on known lemur species. All this feeds into the current lemur conservation status reassessments.

The basis of the cyclical process is information that the IUCN specialist groups gather from researchers and their field studies. The researchers can either be university based, NGO’s or privately funded ones. The field data are assessed according to an extensive set of evaluative quantitative criteria, including: population size; the risk of continuing decline in total population size; and the degree to which the species under consideration now exist in small and relatively isolated subpopulations, as these subpopulations are at a greater risk of going locally extinct.

Species were broadly categorised as “endangered”, “vulnerable”, “rare”, “indeterminate”, or “other”. But, since the mid-1990s, a quantitatively-based conservation status assessment process has instead been adopted. This developed out of internal review of the species conservation assessment process. The current assessment practice places a premium on using up-to-date quantitative field data to the greatest extent possible. Species are now classified as either: “data deficient”, least concern”, or as falling into one of the “threatened” categories, “vulnerable”, “endangered”, or “critically endangered”.

It’s not unusual that for a given species the desired quantitative data are simply not available or known. In such cases, the IUCN still encourages that:

the absence of high-quality data should not deter attempts at applying the criteria, as methods involving estimation, inference and projection are emphasised as being acceptable…

This is where the role of research experts really comes to the fore. Researchers who have conducted recent field studies can provide relatively up-to-date insight on situations regarding species, even though these data may not yet be published. For many species groups, including lemurs, it’s a relatively short list of researchers who fit that bill.

So, to some extent, it’s a case of either using on-the-ground knowledge of the species or site knowledge of those experienced researchers, or attempt to arrive at conservation assessments without their expert input. But it also depends on who is in the room when the assessments are made.

Important lists

This reliance on expert input, while recognised as being of key importance, has also recently come under criticism for not also employing evidence or proper process in making decisions.

But, because swift conservation action is seen as crucial to the overall process, the central role of expert researchers in determining the conservation statuses of species will continue in the future.

The IUCN Red List is not the only endangered species list out there. For example in the primate world, the International Primatological Society produces a biennial review report with the IUCN looking at the 25 most endangered primates.

The ConversationThe next one will be released after the Congress of the International Primatological Society in Nairobi. It will show how important these lists are to raise public consciousness of the threats that primates face, and the conservation efforts used to address them.

Ian Colquhoun, Associate Professor of Anthropology, Western University

This article was originally published on The Conversation. Read the original article.