Biodiversity monitoring in Madagascar: highlights of Manombo’s unique ecosystem
Rainforests are the most biologically diverse ecosystems on Earth. The level of biodiversity – the number of different kinds of life – varies from place to place. Rainforests found on islands are especially known for their biodiversity because the isolation of an island can allow organisms to evolve in their own, unique ways.
Nowhere on Earth has more one-of-a-kind species than Madagascar. This island separated from the African continent about 160 million years ago, giving its life forms time to explore remarkable evolutionary paths. More than 90% of the plant, mammal, reptile, and amphibian species on Madagascar are endemic, meaning they live nowhere else.
Manombo Special Reserve, a coastal rainforest in southeastern Madagascar where Health In Harmony works with rainforest communities, demonstrates the outsized contribution of island rainforests to global biodiversity. Approximately half the size of the city of San Francisco, this coastal rainforest is home to more than 186 land animal species – and that’s not counting insects, spiders, and fish. Several species can be found only in Manombo Special Reserve and the surrounding forest fragments, making this ecosystem incredibly valuable for preventing extinction and protecting the delicate balance of the earth’s biosphere.
Yet, factors such as food insecurity, climate change, extreme weather, and poor access to healthcare can drive conflict between people and ecosystems. The threats to Madagascar’s rainforest include fires, logging, swidden (sometimes known as “slash and burn” agriculture), and hunting — all of which are rooted in communities’ needs for food, healthcare, education, and livelihoods. In fact, Madagascar as a whole is one of the most vulnerable countries in the world when it comes to deforestation and climate change.
To support communities and their stewardship of Earth’s invaluable rainforests, Health In Harmony recently led an initiative to track biodiversity in Manombo Special Reserve, with incredible results that further demonstrate the value of this region and contribute to its protection.
“At a moment when we are desperate to address the climate and nature crisis in tandem, community-designed solutions have boundless potential. Showing their impact on biodiversity through a comprehensive analysis [supports] confidence and investment in these solutions.”
Keep reading to find out more about biodiversity monitoring in Manombo Special Reserve, how each method works, and how communities are designing solutions to ensure this rainforest has a future.
Understanding Manombo’s biodiversity
To protect an ecosystem, one must understand it. Nobody understands the forest better than the people who live within and around it. With this in mind, Health In Harmony partnered with the communities of Manombo Special Reserve and academic collaborators to listen to the rainforest and understand more about the multispecies life who call it home.
Given that different species have different needs and causes for population change, by studying species distribution and abundance, it is possible to assess the overall status of the reserve—such as whether the rebound of a once-endangered species indicates regeneration of the forest as a whole.
From August 20th to October 8th, 2023, Health In Harmony worked with community members and Niry Samahazary, a graduate student from the University of Toamasina, to track biodiversity within Manombo Special Reserve. The team brought together two methods: ecoacoustics, measured through sound recordings, and environmental DNA, collected through water samples. The results were astoundingly positive, with more than 100 species detected, several of which are endemic, threatened, or both.
By combining two monitoring strategies, the team covered gaps between the methodologies and got a holistic picture of biodiversity in the canopy, on the forest floor, and in the abundant freshwater. As a long-term measure, biodiversity monitoring allows communities to track how their initiatives can bring back rare and culturally significant species.
Ecoacoustics
Ecoacoustics is the science of studying sounds produced by animals in their natural environment. Although humans cannot begin to grasp the nuanced meanings held within animals’ calls, barks, chirps, wails, and songs, we can at least use these sounds to understand what habitats different species depend on.
Using ecoacoustics to monitor biodiversity has advantages over conventional methods such as setting traps, walking transect lines, and chasing lemurs through the forest. One benefit is that audio recorders can collect data continuously for several weeks. Another is that ecoacoustic monitoring is neither invasive nor disruptive: animals barely notice the palm-sized recorder hanging from a branch.
One of Manombo’s noisiest residents, the Maromandia stump-toed frog (Stumpffia tetradactyla), is as small as it is loud. Males grow to less than an inch long, and females are unknown. The frog wears a perfect forest-floor mottling of beige and brown, with a line down the spine to mimic the central vein of a leaf. This is all very good for camouflaging from predators—and it also makes this species nearly impossible for scientists to spot. The Maromandia stump-toed frog is listed as “data deficient” by the International Union for Conservation of Nature (IUCN), meaning researchers have yet to understand where it lives across Madagascar and whether it is endangered. The frog calls recorded in this study will help fill this gap. For now, at least, it suggests this species is thriving in Manombo Special Reserve.
Listen to one of these recordings here:
Over seven weeks, the team recorded 160,000 minutes of audio in 34 locations of Manombo Special Reserve. In thousands of vertebrate audio detections, 50 different species were identified, five of which are listed as threatened, endangered, or critically endangered by the IUCN.
The recordings offer a glimpse into the behavior of shy forest animals. You may be familiar with the term “dawn chorus,” the crescendo of bird and mammal song that happens just before sunrise. This phenomenon was clear in the ecoacoustic data, which showed 36 species vocalizing in the cacophonous hour from 5 to 6 am, and only six species making noise in the still, quiet dusk from 7 to 8 pm.
eDNA
Environmental DNA, also known as eDNA, is the genetic material shed by living organisms in the environment. It can come from hair, scales, mucus, stool, urine, spores—anything that washes off an organism in the rain and collects in a pond or puddle. Like ecoacoustics, eDNA is a non-invasive monitoring technique. By spending only a few days collecting water samples, researchers can paint a comprehensive picture of the forest’s terrestrial and aquatic biodiversity.
A team of rainforest community members, graduate students, park agents, and Health In Harmony staff collected water samples from 29 locations within Manombo Special Reserve in August 2023. From those samples, researchers detected 113 species, including 10 threatened with extinction, such as the critically endangered black-and-white ruffed lemur (Varecia variegata). More often heard than seen, as their croaks and barks echo through the forest. This lemur is highly sensitive to deforestation due to its need for fruit-bearing trees that are also desired by loggers, and its preference for living in small family groups in the high canopy. Its population has dropped by as much as 80% in the last two decades.
Manombo Special Reserve is one of the most important remaining habitats for black-and-white ruffed lemurs, meaning that protecting this rainforest from further degradation is essential to support the lemur’s population size, genetic diversity, and survival.
How? Manombo communities have designed creative solutions to produce more food on less land, eliminating the need to cut and burn forest to grow more crops. Since 2019, thousands of community members have participated in intensified rice agriculture training, boosting the yields from existing fields. Now, communities are experimenting with insect protein farming and fish-rice aquaculture to generate dietary protein without the extensive land-use required by livestock such as cattle. These solutions are extremely important for the survival of black-and-white ruffed lemurs and all their relatives.
Take a moment and listen to this lemur call:
The role of biodiversity
“In the past, Madagascar was covered by forest, but most of those forests have disappeared. But the forest in Manombo has not disappeared completely... This forest is what makes Madagascar unique. It is our wealth.”
Nature’s strength comes from its diversity. In Madagascar, animals such as the black-and-white ruffed lemur disperse trees by eating fruits and depositing their non-digestible seeds in new corners of the forest. These fruit trees provide habitat for many species of wildlife and are used by people for timber, food, and medicines. Seeds dispersed by lemurs have higher germination rates than those that fall from the tree. The rainforest needs its gardeners.
Both ecoacoustics and eDNA detected the Manombo sportive lemur (Lepilemur jamesorum), endemic to this one parcel of rainforest and one of the world’s most endangered primates. This lemur’s survival is threatened by trapping for the exotic wildlife trade. To ensure the species survives, Manombo rainforest communities have designed programs to secure income without needing to trap lemurs, birds, bats, or other wildlife. Some communities have focused on beekeeping to produce honey, while others are experimenting with agroforestry of crops such as vanilla, cloves, and black pepper. To grow a source of timber for building houses without needing to log in the rainforest, communities have included native timber species such as Malagasy rosewood (Dalbergia maritima) and varongy (Ocotea racemosa) in their agro-forests.
Equipped with the maps from ecoacoustics and eDNA, Manombo rainforest communities and Health In Harmony can now identify the most important habitats used by each wildlife species and use this information to plan strategic reforestation. Take, for example, the rusty-grey lesser bamboo lemur (Hapalemur meridionalis), listed as vulnerable by the IUCN. Like the giant panda of China, this lemur depends entirely on bamboo for its diet. This lemur’s chittering banter appears frequently in the ecoacoustic data, but the detections are not spread evenly across the forest. Most are from a particular forest fragment next to a pair of villages. By identifying hotspots where the bamboo-lemur can be heard, community members from these villages can work with Health In Harmony to include native Malagasy bamboo in their agroforestry plots. Not only can bamboo be used to build housing, it can also regenerate habitat for this unique lemur.
Learn more and get involved
The rainforest of Manombo is stewarded by around 12,200 people living in balance with this ecosystem. The edges of the forest are frayed, and the wildlife lives in isolation from other populations due to hundreds of years of deforestation. In 2019, very few households around Manombo had access to safe drinking water, latrines, medical care, sufficient food, or secondary education. Today, the rainforest communities of Manombo are nursing the rainforest and its biodiversity back to health. Through Radical Listening, communities have designed innovative healthcare delivery through mobile clinics, agricultural training programs, protein production through black soldier-fly farming, rainwater harvesting to obtain safe drinking water, and sustainable income streams. As the community thrives, so does the forest. And as the forest thrives, human health improves.
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