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How Small is Too Small?

Posted on Apr 30, 2018

Madagascar’s total forest cover fell by 40 percent in the second half of the 20th century, but fragmentation of the forests that remained progressed even more quickly.

How Small is Too Small? / Mongabay, October 18, 2017

The Fragmented Forests of Madagascar / NPR, November 26, 2017

ANKAFOBE, Madagascar — When he first told colleagues at the Missouri Botanical Garden that lemurs still lived in the forest in Ankafobe, Jean Jacques Rasolofonirina said he was met with disbelief. “The forest is too small,” he recalled one saying—just 27.76 hectares, to be exact, split into three fragments scarcely larger than three or four New York City blocks.But these narrow wooded valleys still hold three species of lemurs, and owls, frogs, and bats besides. Solofo, as friends and colleagues call him, rattled off their Latin names as he walked down the narrow path that enters the forest from the main road. He stopped to mimic the call of a Malagasy paradise flycatcher (Terpsiphone mutata) perched on a nearby branch, and pointed out seedlings planted to fill in a small clearing beside a stream.After a few minutes, he gestured at a gnarled, windswept tree at the edge of the woods with smooth gray bark and small, waxy leaves. “That,” Solofo said, “is the sohisika,” or Schizolaena tampoketsana, one of a handful of plant species found nowhere on the planet outside the rolling grasslands here, in a single district northwest of Madagascar’s capital city, Antananarivo.

Sohisika trees, represented by roughly 200 to 300 mature plants all told, are considered to be at high risk for extinction. Ankafobe holds just 15 of them, protected since 2005 as the centerpiece of the 150 hectare community reserve The reserve is supported by the Missouri Botanical Garden (MBG) and is now in the process of achieving legal designation as a New Protected Area.The other sohisikas are scattered on the savannah surrounding the reserve and in a handful of green slivers that mark the clefts between neighboring hills — areas with no environmental protection and that face the constant threat of brush fires during the dry season. Until 2014, another 50 of the trees could be found a few miles away at a site managed by the Antananarivo-based group Madagasco Environnement. But recent satellite imagery shows that the valley where the sohisika were concentrated is now mostly bare.As logging, charcoal production, and the clearing of woods for farmland took their cumulative toll on Madagascar’s forests in the second half of the 20th century, the country’s total forest cover fell by 40 percent. But fragmentation of the forests that remained progressed even more quickly. Between 1950 and 2000, there was an 80 percent reduction in the area covered by “core forests,” which lie at least one kilometer from the nearest edge, a trend mirrored in forests around the world.The result has been a splintering of remaining habitat for endangered species across Madagascar, and a scramble among conservationists to figure out how best to protect what’s left.

“The tragedy of Madagascar is that the forest there is in pieces,” said Stuart Pimm, an expert on the biology of fragmentation and extinction who teaches at Duke University in North Carolina. “When it comes to fragmentation, there’s bad news, there’s worse news, and there’s worse news still.”

As the size of a given patch of forest dwindles, Pimm explained, its basic geometry changes too, so that there is much more “edge,” or perimeter, for each hectare of forest. It’s similar to what happens when a child cuts a single sheet of paper into a paper snowflake. These multiplying forest edges make it easier for predators to reach their prey under the canopy, expose trees more readily to the effects of drought, and give brush fires purchase in forests they wouldn’t otherwise burn.


“It’s either small or nothing”


“Bigger is always better,” Chris Birkinshaw, lead botanist for MBG’s Madagascar Program, told Mongabay, “but sometimes you don’t have the choice: it’s either small or nothing, and that’s certainly the case with some of our areas.”

Some of Madagascar’s most fragmented ecosystems are also among the most critical to global biodiversity. Madagascar’s evergreen littoral forests grew up on old sand dunes and once stretched in an unbroken band two or more miles thick along the whole of the island’s 1,000-mile long east coast. Today, Birkinshaw said, “Most of that vegetation type is gone: there’s no fragment now which is bigger than 2,000 hectares.” Still, researchers estimate the remaining fragments of evergreen littoral forest contain 13 percent of the island’s plant species on less than 1 percent of its land.

Dry deciduous forests in the west and the varied woodlands on the central plateau, too, have been reduced to tiny fractions of their former ranges. This degradation, in turn, has combined with Madagascar’s unique evolutionary history — more than 50 million years of natural selection in isolation from the rest of the world — to produce a growing number of species with tiny known ranges. Some of them are as small as a couple square miles. 

Missouri Botanical Garden botanists began to consider doing conservation work alongside their research in Madagascar nearly 20 years ago. “When we thought about it, all the NGOs in Madagascar were interested in big blocks of forest that required [major] funds,” explained MBG’s country director, Christian Camara. Yet dozens of globally unique ecosystems remained outside of Madagascar’s protected area network. “We realized that there are some very important plant species in those small blocks of forest, and nobody was caring for them,” he said.

In 2000, an MBG review of priorities for plant conservation around the island produced a list of 78 sites. Today, half of the 78 have been integrated into existing or new protected areas, including the 12 sites managed by MBG. The other half remain without environmental protection, and at least one has been destroyed. Some are quite large — MBG’s largest site is over 75,000 hectares — but each of these areas, particularly the smallest, like Ankafobe, serves as a kind of natural history museum.

“If you’re wanting to know what [that forest] was like, what you’ve got is what you’ve got,” Birkinshaw said. “If it’s little, it’s little, and how viable that will be will depend on how much we can intervene.”

“So we’re probably getting into the realm of, to a certain extent, gardening—intensive management—and if that’s what’s necessary, that’s what we’ll do, if we can get funds for it,” he added.

Large protected areas carry their own challenges: the logistics of traveling throughout a remote area, the political maneuvering required to align the interests of many different groups, and the basic costs of running any kind of research or development program across a large swath of rural Madagascar.

“The bigger the site is, the more communities you are going to have to deal with,” said Julie Razafimanahaka, director of the Malagasy conservation group Madagasikara Voakajy, which manages seven protected areas in small forest fragments. “Probably, also, more generally, the more difficult the access to the entire area. And if you don’t have the resources — like people and money — to cover the area, there are very high risks that you will have lots of illegal activities happening for the site, and the less likely that you’ll have the reports on these illegal activities on time.”

On the other hand, Razafimanahaka explained, “In the smaller sites, you have to treat all the threats seriously.” Such was the case, for example, with reports that exotic pet collectors were operating near Voakajy’s smallest site, 90 hectares of forest near the village of Tarzanville, which gave its name to the critically-endangered Tarzan’s chameleon (Calumma tarzan). “Any threat is high-intensity,” she said.

“Large site, big problems,” MBG’s Christian Camara said. “Small site, small problems.” But in a site as small as Ankafobe, almost any problem can become an existential one.


Keeping fire at bay


Solofo’s main problem is fire. “It could be farmers, it could be lightning, it could be bandits stealing cattle and trying to cover their tracks,” he said. Sometimes truckers and bus drivers stop to cook by the side of the road and neglect to put out the embers when they leave. One way or another, during the dry season, there is always fire.

Exactly what the hills around Ankafobe might have looked like before the first humans arrived in Madagascar about 2,000 years ago is still the subject of some controversy. If native grasses formed any part of the landscape, as many scientists now believe, it’s likely that fire was a common occurrence.

“The problem with the situation today,” noted Marina Blanco, a Duke University primatologist who has studied mouse lemur populations in Ankafobe, is that the whole region is characterized by what she called “extreme fragmentation.”

“In vulnerable and sensitive habitats,” she wrote in an email, “small disturbances cause dramatic effects, as there are no buffer zones and local extinction is an omnipresent threat.”

Solofo and the community group he chairs, VOI Sohisika, have managed Ankafobe on a shoestring budget since 2005, maintaining a nursery for native plant species and clearing fire breaks on the crests of the hills that surround each of the three small blocks of forest. Along the way, they’ve rallied a growing number of their neighbors to the cause as villages in the area have seen sediment from erosion fill their rice paddies and watched their water sources dry up as streambanks are cleared of trees. The association, which began with a few dozen members representing 15 percent of the surrounding community, now claims over 300, more than 90 percent of adults in the local fokontany, the smallest unit of government in Madagascar.

Fara Rajajarohavana lives along the road beyond Ankafobe with her husband Maxim and their children. They moved here from their hometown, Ambositra, in 2001, looking for more land to farm. Back home, Maxim said, “The land stays the same but the population is growing.” For the first several years near Ankafobe, they watched as fire whittled away at forest fragments in the surrounding hills, then joined VOI Sohisika soon after the group was formed.

“We became part of the association for the future of our children,” Fara said. “Because, if the forests disappear, the water will disappear, and our children will be poor.”

Last year, members of VOI Sohisika grew 45,000 seedlings in Ankafobe’s nursery, the continuation of a decade’s work to expand its fragmented islands of green to the the surrounding hills and reconnect them to one another. They’ve planted avocado and orange trees to grow orchards that can help fund the group’s restoration efforts, along with quick growing-shrubs (Tephrosia vogelii and Crotalaria retusa) to use as green fertilizer for the native plants. And, Solofo said, they have planted more than 3,000 sohisika seedlings that are gradually expanding the tree’s range once more.

In 2014, close to half their work was wiped out over the course of a few windy days at the end of October. When a brush fire crossed the Manankazo River and spread upwards to the edge of Ankafobe, two hundred members of the association were waiting on the hill to extinguish the flames with green branches and buckets of water. But they could only hold it off for so long: by the end of the week, the fire scorched the seedlings they’d planted between 2008 and 2013, and nine hectares of the forest besides.

It was a demoralizing blow. “At first, we felt like giving up,” said Maxim Rajajarohavana. “But we got hope replanting the forest, and seeing the work of other members of the VOI, the progress made after 2014,” he said.

In July, Solofo stomped through the underbrush at the forest’s periphery and pointed to the scare-crow like trunks of some of the fragment’s largest trees. “You see the big dead trees there?” he said, surveying the damage. “That’s because of the fire.” Beyond them, exposed red cliffs marked the seven landslides that sent cascades of clay and rock into the ravine below in the fire’s wake.

Since then, the members of VOI Sohisika have redoubled their efforts, pre-positioning water barrels and planting hedgerows that Solofo hopes can act as green firebreaks. At the start of each dry season, they clear 14 miles of firebreak by hand, using hoes to scrape two narrow alleys clear of all vegetation, and burn the 30-foot-wide strip of grass between them. This is the sweat equity members pay into the association. MBG pays a stipend of 5,000 ariary, about $1.60, for a day’s work, while each member contributes 10 percent of what they earn to VOI Sohisika. Solofo said clearing firebreaks consumes about a third of his $3,500 annual budget. The rest goes to paying patrollers who work in pairs during the dry season, along with two full-time nursery staff, Solofo himself, and two research assistants who work with MBG on collecting ecological data.


Making fragments whole


The risk that both animates this work and threatens to make it obsolete is that continued fire could push these fragments below some basic threshold of ecological viability.

Even relatively large fragments suffer from what is usually referred to as “pauperization,” a process that leads isolated chunks of habitat to lose the bulk of their biodiversity over time, because of fire, predation, genetic bottlenecks, or some other form of attrition. Different kinds of plants and animals respond to these pressures differently, but Pimm, the extinction expert, said that the animal species that do remain in fragments as small as Ankafobe may be living on borrowed time.

Pimm has been a co-author of several studies of the planet’s longest-running experiment on fragmentation in the Brazilian Amazon, where the biologist Thomas Lovejoy has been observing forest plots of one, 10, and 100 hectares since 1980. “At least for bird species, which we know the best,” Pimm explained, “a fragment of a hectare loses most of its bird species in two or three years, 10 hectares in under a decade, 100 hectares in maybe 10 to 20 to 30 years. You need to have a fragment of close to 10,000 hectares before you have a chance of keeping those species for the long-term.”

“And that’s why,” Pimm added, “in the paper we published recently, we argue that re-connecting fragments is one of the most cost-effective conservation solutions we have, because it dramatically slows down the rate of extinctions.”

That paper built on work Pimm has done with the U.S.-based group Saving Species in the coastal forests north of Rio de Janeiro, Brazil, to plant forest corridors that stitch together remaining fragments home to the endangered golden lion Tamarin (Leontopithecus rosalia). A similar effort is underway in southeastern Madagascar, where the Antananarivo-based Madagascar Biodiversity Partnership is trying to create a four-and-a-half-mile forest corridor to reconnect fragments of lowland rainforest east of Ranomafana National Park.

Once upon a time, it’s thought that Ankafobe was part of a contiguous mosaic of forest that connected it to the Ambohitantely Special Reserve, seven miles to the west, which contains some of the last primary rainforest on Madagascar’s central plateau.

Solofo spoke excitedly of a “circuit touristique” where visitors, both Malagasy and foreign, could step off the road and hike to a waterfall that lies at the opposite end of the preserve.

After all, one advantage fragments often hold over larger, more remote forests is their accessibility.

“Don’t forget,” said MBG’s Chris Birkinshaw, “most Malagasy might never have seen a lemur in the wild.” Here, less than three hours from Antananarivo, they still can. “Any opportunity to strengthen connections between Malagasy and their natural heritage is well worth doing,” he said, “because if you fail to do that, then, well the future isn’t very bright anywhere in Madagascar.”

Solofo said that the oldest people living in Andranofeno, just north of Ankafobe, can still recall a time when the three fragments in the preserve were all connected. If VOI Sohisika’s work persists, there’s a chance the youngest will see them reconnected once more.