Virtual field trip to the Guajira desert and the Serranía de Macuira in northern Colombia

James and Thibaud Aronson describe the natural and cultural context of a little-known area of northern Colombia, home to the Wayuu people and a microcosm of arid lands worldwide.

Colombia is one of the world’s seventeen megadiverse countries.  In a few hours of travel, one can go from the sweltering Amazonian lowlands to the snow-capped peaks of the Andes. It even has a true desert, a small peninsula called la Guajira, shared with Venezuela, which constitutes the northernmost point of South America.

For most of the last 50 years, the Guajira was notoriously dangerous, principally because of drug trafficking, but things have improved in recent years. We traveled there last month, shortly after the first big rains the region had received in several years. ​ And we found that it’s a poignant example of the plight of drylands globally and their peoples.

Guajira02_26_2019_map

The Guajira peninsula, in northern Colombia, including the authors’ itinerary.

Our trip actually began in Panama, which was part of Colombia until 1903. While much smaller, Panama is also a country of contrasts. Much of the Pacific coast used to be covered in seasonally dry tropical forest, and some fragments persist today in and around Panama City itself, while the forests of the Caribbean slope, a mere 50 km away, are much wetter. A curious switch occurs near the Colombian border, where the wet forests then extend down the Pacific coast of Colombia and Ecuador – the famous Chocó-Darien rainforest, one of the wettest and most diverse tropical forests on Earth.

Meanwhile, the seasonally dry forests continue along the 1,000 km long Caribbean coast of Colombia and give way to semi-desert and then true desert (annual rainfall < 250 mm), lined by a coast with mangrove forests, and a series of lagoons and bays where flamingos and ibises add a shock of color.

IMGP2432

Mangroves in Bahia Hundita, Alta Guajira, showing desert woodland with tree cacti (Stenocereus griseus) and various legume trees growing on the sandstone bluffs in the background.

6Z1A5797

Roseate spoonbills, great egrets, and a white ibis sharing a coastal wetland near Uribia.

As if this wasn’t enough contrast, halfway along the Caribbean coast rises the Sierra Nevada de Santa Marta, Colombia’s tallest mountain range, reaching 5,700 meters (18,700 feet) above sea level at the highest peak. It takes only about two hours to drive from its foothills, where toucans and monkeys chatter in the majestic trees, to Riohacha, the gateway to the desert.

6Z1A3879

A brown-throated three-toed sloth (Bradypus variegatus) hanging by one arm in a Cecropia tree in Tayrona National Park, at the base of the Santa Marta mountains.

Alta Guajira’s desert trees and woodlands

The Alta Guajira is arid indeed, but it hosts trees, remarkable both in their exuberant diversity and their abundance, considering the high temperatures and meager rainfall. We saw what we consider true desert canopies, such as we have described in other posts. However, no desert flora exists in isolation, and indeed the kinship to the ecosystem type known as Seasonal Dry Tropical Forest (SDTF; see map above) seems to be strong.

The dominant trees of the Guajira are species of Prosopis, Caesalpinia, Vachellia (formerly part of Acacia s.l.), Parkinsonia and other legume genera, accompanied by Bursera, Capparis relatives, Bignoniaceae, and other species common in the dry forests of Central and South America, and 3 kinds of tree cacti (Stenocereus, Pilocereus, and Pereskia), growing close together, often covered in climbing vines. In particular, it was interesting to see bona fide desert woodlands dominated by two well-known legume trees, Prosopis juliflora and Vachellia farnesiana, which are widespread and often strongly invasive in other parts of the world, but not here! Fascinating biogeographical and ecological questions abound in this poorly explored region, many of which are relevant to conservation and restoration.

Regarding  landscape ecology in the region, the vegetation is curiously like a patchwork, alternating between dense desert woodlands, nearly pure tree cacti stands, sometimes with a dense grass cover, and sometimes not, and frequent saline flats where nothing grows. In our opinion, the human element, namely land and resource use history, is paramount to understanding what one sees when travelling here and trying to ‘read’ the landscapes.

IMGP1364

Mixed patch of tree cacti and spiny legume trees with a surprising amount of grass understory. Elsewhere under similar stands, for no clear reason, there is no grass cover at all.

IMGP2305

A track of the Alta Guajira, near Nazareth, at the base of the Macuira hills where the notorious Prosopis juliflora, known in Colombia as Trupillo, is so exuberant and long-lived it forms a natural tunnel above this track.

 

IMGP1037

Prosopis juliflora colonizes newly exposed beach dunes, in areas where the shoreline is receding. Here, at Camarones, it occurs alongside Calotropis procera, a woody weed of the Apocynaceae known in English as giant milkweed, and familiar throughout the Caribbean islands, the Middle East and drylands of Africa. It survives because of its toxic milky latex where most other plants get eaten out by livestock.

Other standouts are the beautiful Palo de Brasil, Haematoxylum brasiletto, with its unusual fluted trunks and Pereskia guamacho, an enigmatic ‘primitive’ tree cactus with true leaves and one of the most exquisite tasting fruits we know. This is one of the least well-known but most intriguing of all desert trees to our minds.

IMGP1656

Typical landscape of the northern Guajira desert woodlands, with an even-aged stand of one of the several neotropical legume trees known as Brazilwood: Haematoxylum brasiletto, or Palo de Brasil in Spanish.

Despite those common names, this species is in fact only found wild along Caribbean coastlines from Colombia and Venezeula, all the way north to both coasts of Mexico. The scientific name is thus a misnomer. The most famous Brazilwood tree is another legume, Paubrasilia echinata (= Caesalpinia echinata) that once grew abundantly along the Atlantic coast of Brazil, as a large tree with a massive trunk, reaching up to 15 meters tall. Today, it’s almost entirely gone in the wild, and mostly planted in gardens and along roadsides. It was prized for the bright red dye obtained from the resin that oozes from cut branches or trunks. The dye was widely used by textile weavers in the Americas and Europe in the 17th-19th centuries. The tree also provided the wood of choice for high quality bows for stringed instruments and was widely used for furniture making as well. So important was its economic value that the country was named after it, originally Terra do Brasil (Land of the Brazilwood), later shortened to Brazil. Recently it was designated as sole member of a new genus, as part of a comprehensive revision of the entire genus Caesalpinia, carried out by an international team of experts.

It’s curious that H. brasiletto bears the same common name as P. echinata, since the two trees are nothing alike, apart from their red sap and heartwood. Little literature exists for H. brasiletto, and we are embarking on some detective work to shed some light on this puzzle. We go into detail as these are both relatively fast-growing trees with great economic as well as ecological value. They would both be excellent candidates for inclusion in ecological restoration work and are both in dire need of conservation efforts.

Wayuu: Alta Guajira’s Indigenous People

This desert also hosts a fairly large human population. The Guajira is the home of the Wayuu, Colombia’s largest surviving indigenous group and, along with the Navajo, one of the last desert-dwelling peoples in the New World. These fiercely independent people, organized in 17 matrilineal clans, were never subjugated by the Spanish, and even today the Guajira region functions mostly in isolation from the rest of the country. As we were heading well off the beaten track, we needed a guide, a 4 x 4 jeep in good condition, and a skilled driver to navigate the meandering and unmarked desert paths.

Despite an ancient history of human presence, and some periods of intensive exploitation and intervention (such as a pearl harvesting boom that took place soon after European explorers arrived), the ecological condition of the region at the landscape scale is remarkably good. Indeed, apart from the salt works in the small town of Manaure, which produce two thirds of Colombia’s salt, and El Cerrejón, South America’s largest open-pit coal mine, in the south of the Guajira, there is no major industry.

IMGP2473

Typical traditional salt works at Manaure worked by hand by local men and women just as they have for generations.

And the isolated people who dwell here – fishermen, shepherds, and weavers – are right out of a Gabriel García Márquez story. Indeed the author, most famous for One Hundred Years of Solitude, grew up on Colombia’s northern coast, speaking both Spanish and the Wayuu language, Wayuunaiki. As we traveled deeper into the desert, we traversed small settlements with simple houses made of wood and yards surrounded by tree cacti hedges.

IMGP0996

The Wayuu village of Boca de Camarones, in the south of the Guajira peninsula, showing the living hedgerows of columnar cacti produced from tall stanchions. In the background, surrounding the homes, are Trupillos, and good specimens of Dividivi Libidibia coriaria (formerly called Caesalpinia coriaria).

This third caesalpinoid legume tree, closely related to the two Brazilwoods mentioned above, is the source of another lovely red dye, derived in this case from its pods. Until recently, there was an annual festival in Camarones, in honor of this formerly major economic plant product. The tree was also used as an important source of tannins. Like Paubrasilia echinata, it deserves more ethnobotanical and biogeographical studies.

Here, as in many other arid lands, goats and sheep are important for the Wayuu people, as a source of food and social currency. For example bride price during arranged weddings, and gifts for guests attending vigils of important elders and healers, are paid to this day in heads of live goats or sheep. Historically, mules and donkeys were very common as well, but now they are increasingly replaced by motorcycles.

IMGP0993

Small children following a flock of desert-hardy sheep in Boca de Camarones. The peaks of the Sierra Nevada de Santa Marta are visible in the background.

Crown jewel of the Alta Guajira

The crown jewel of this desert, its best kept secret, is the Serranía de la Macuira, a small mountain range (serranía meaning “small sierra” in Spanish) in the northeast of the peninsula. This miniature sky island is almost impossibly lush, thanks to moisture-bearing clouds that shroud its upper reaches. They feed streams that flow year-round, and sustain many kinds of trees that grow to well over 10 meters tall.

As one climbs the slopes of the Macuira, the humidity dramatically increases and the parched lowlands, with their desert woodlands, blend perceptibly into a seasonally dry tropical forest reminiscent of those we had seen in Panama. A little-known fact: seasonally dry tropical forests are the most endangered of all tropical forest types, and those in La Guajira are worthy of much greater research, conservation, and restoration.

Climbing higher still, the mid- and upper ranges of the Macuira seem like another world. Most astonishing of all, there is apparently an abrupt transition above 550 meters, and the higher reaches are covered in true cloud forest, with mosses, epiphytic orchids, tree ferns, and dozens of tree species that otherwise occur hundreds of kilometers away! This is probably the only place in the world where cloud forest is found less than 5 km from true desert. Fortunately – from a conservation point of view, but unfortunately for us – the upper peaks of all three peaks of the Macuira are sacred to the Wayuu, and completely off-limits, to native people and visitors alike. Try as we might, we were unable to get permission to hike up there.

IMGP1967

IMGP2002

Seasonally dry tropical forest on the northeastern facing slope of the Macuira, where precipitation is much higher than in the surrounding lowlands occupied by desert woodlands.

Even though the whole Macuira is officially protected as a national park, the reality is more complicated. While walking inside the park, we encountered recently cut trees, the ubiquitous goats, and even a Wayuu man hunting birds with a slingshot in broad daylight. The beautiful continuous tree canopy covering most of the slopes stands in stark contrast to the severely eroded, nearly bare hilltops, on which stand small Wayuu homesteads. Still, the presence of clear ecotones speaks to mostly healthy landscapes.

IMGP1898

The severe erosion around a small Wayuu farm inside the Macuira National Park.

Alta Guajira’s ecological future

The pressures on the Guajira’s ecosystem health include a large mine (El Cerrejón, mentioned above), overgrazing by domestic livestock, and stark poverty facing the native people and more recent immigrants. But there are positive factors as well. There are progressive laws in Colombia related to ecological restoration. Moreover, since 2012, Colombia has a National Restoration and Rehabilitation Plans (pdf), as well as a Law of Remediation, which imposes large environmental offset payments from large-scale development projects (like hydroelectric dams) to underwrite conservation and restoration work. Moreover, the national park system, within its network of 56 protected areas, harbors populations of almost half of the 102 indigenous peoples in the country, and in the case of Macuira, this is clearly not just a paper park idea.

Still, the national park (25,000 ha in size; officially designated in 1977), operates with a skeleton staff attempting to carry out an ambitious management plan (pdf) despite an insufficient budget. Staff and volunteers provide short tours to day-visitors, and maintain some fenced-off livestock exclosure plots, where they are studying natural regeneration. Daily interaction with the Wayuu living in the park appear to be harmonious, and indeed there is a clear sense that part of the Park’s mission is to restore and protect the Wayuu people’s natural and cultural heritage. Recently, the Instituto Humboldt, Colombia’s stellar national research institute, has established permanent plots in the Macuira range as part of a series of 17 plots including all the tropical dry forest types in Colombia. In the Macuira, this work is done in collaboration with botanists from the Universidad de Antioquia, in Medellin. Furthermore, researchers at Kew, the Smithsonian Institute, and many conservation NGOs are all developing collaborations with the Colombian government to explore and help the country move forward with green development.  The Missouri Botanical Garden also has long-standing MoUs for joint research with 3 different institutions in Colombia, with bright prospects for deepening cooperation in the future.

Like many indigenous peoples around the world, the Wayuu are at a crossroads. Their language and some of their traditions are still alive and well, but others have already faded. There are few legal sources of income in the harsh desert, the ancestral Wayuu land. How will they manage in the future? What can they do to adapt?  Some, like our guide, José Luis, are trying to change mentalities, but they clearly need more help.  As throughout Colombia, there is clear and urgent need to build on the alpha-level studies already underway, and move onto applied ecology, agroforestry and land management programs, including community-based restoration programs and ecotourism in conjunction with the national parks.

IMGP2197

Our Wayuu guide José Luis Pushaina Epiayu (on the right) and Macuira park ranger Ricardo Brito Baez-Uriana (on the left), talking about birds with a local Wayuu family.

 

Advertisements

What does the Black-faced Antthrush tell us about tropical forest restoration?

Anna Spiers (University of Colorado Boulder) describes a recent field experiment done with Emma Singer (Hamlin College) and Leighton Reid (CCSD) during an Organization for Tropical Studies Field Ecology Course in Costa Rica.

Bird diversity and forest restoration are synergistic. Birds facilitate forest regeneration through seed dispersal, pest control, and pollination. Forest restoration replenishes lost bird habitat by providing food, protection from predators, and suitable territory for breeding and nesting. Monitoring bird communities in a regenerating forest is an effective strategy to gauge the success of restoration.

While some birds are flexible regarding the quality of their habitat, others require a narrower set of conditions to survive. One such bird is the Black-faced Antthrush (Formicarius analis), a medium-sized, ground-dwelling insect-eater, easily distinguished by its plaintive song and chicken-like strut. The bird spends its days flipping over leaves and sticks with its bill to expose tasty ants, beetles, and other arthropods (and sometimes small vertebrates). A member of a bird family highly threatened by forest fragmentation (Formicariidae), the Black-faced Antthrush is known to disappear from small forest fragments and to struggle crossing even narrow strips of open space. Finding such sensitive birds in a regenerating forest is a positive signal that forest restoration is increasing habitat for forest-dependent species.

bfan

Black-faced Antthrush (Formicarius analis) strutting across the rainforest floor. Image: Luke Seitz/Macaulay Library at the Cornell Lab of Ornithology (ML54054261).

Earlier this month, we did an experiment to find out how different forest restoration strategies affect the Black-faced Antthrush. Specifically, we tested whether the bird exhibited a stronger territorial response in tree plantations, naturally-regenerating secondary forests, or areas where patches of trees (tree islands) had been planted to stimulate forest recovery. We expected to find that birds would be more defensive of areas where trees had been planted, given that these areas had a more closed canopy and more leaf litter for the birds to pick through for arthropods.

jlrplayback

Leighton holds up a speaker to conduct a bird call playback. Unsurprisingly, there was no response in this scrubby, abandoned pasture (one of the control points in our experiment). Image: Martha Bonilla-Moheno.

To test the bird’s territorial response, we amplified a locally-recorded sound file of the bird’s vocalization and recorded its response. We noted how long it took for the bird to respond, how many notes it sang in response, and how close it approached the speaker. For this species, a short call with 4 notes is a “hello”, but a long call with upwards of 12 notes is a warning to let the other birds know that this territory is taken.

map

Our study area at Las Cruces Biological Station in southern Costa Rica. Each of the two restoration sites contained a tree plantation, a natural regeneration area, and a “tree island” area where patches of trees were planted to kick-start forest recovery. Image: Google Earth 2018.

Antthrushes defended restoration areas where trees were planted

As we expected, Black-faced Antthrushes responded more quickly and more forcefully when we taunted them with calls broadcast from tree plantations and tree island plantings – an indication that they were expending more energy to defend these areas. However, we only found this at one of the two restoration sites. The other site was a veritable antthrush desert with not a single response during any of our trials. Leighton’s collaborator Juan Abel Rosales often finds Black-faced Antthrushes at both sites, but this second site is near a road and dogs occasionally wander into the regenerating forest, possibly causing birds to temporarily abandon this area.

maxnotesfig

Black-faced Antthrushes responded quickly and with many tooting notes when we played their song to them from tree islands, plantation, and mature forest, but they responded not at all in abandoned pastures or in natural regeneration. The data representing restoration treatments are from one site only – at the other site we recorded no birds during any trials.

Tree islands and plantation had a couple of habitat features that natural regeneration lacked. First, the understory was more open, providing ground-dwelling birds with greater visiblity. Second, planted areas also had deeper leaf litter, and leaf litter is essential for a bird that makes a living flipping leaves to find its dinner.

habitats

Understory comparison between natural regeneration (left) and a tree plantation (right). Both have been recovering for 15 years. Natural regeneration vegetation is thick and still grassy from pasture days. A closing canopy in the tree plantation produced a thinner, more visible understory, with lots of nice leaf litter, full of delicious arthropods.

So what does the Black-faced Antthrush tell us about forest restoration?

 It may be telling us two things. First, restored forests growing up alongside remnant ones can be valuable habitat worth defending. When birds spend time calling, that is time that they do not spend foraging, and they can pay a price with their energy budget. Second, tree planting may create habitat for these birds faster than natural forest regeneration – although natural regeneration is highly variable from site to site, and we only found a pattern at one site right next to an old-growth forest. Promisingly, we did not see a difference between tree islands and the tree plantation, which suggests that we could plant fewer trees and still see the return of a forest-dependent bird species within about 15 years.

For more information about the Islas Project (with the tree islands) see previous NHER posts here, here, and here. Thanks to Bert Harris for some of the ideas that we used in this project!

 

 

How to grow instant fig trees to restore rain forests in Costa Rica

CCSD scientist Leighton Reid and Lyon Arboretum director Rakan Zahawi write about giant fig tree cuttings: how to make them and why some grow better than others.

Choosing the right species to include in a restoration project is a hard choice, but in the economy of nature, some species earn a bigger ROI than others. For example, Pacific sea otters maintain kelp forests by eating sea urchins, and wolves in Yellowstone National Park allow aspen groves to regenerate by scaring away tree-munching elk. These vital creatures are called “keystone species” because they hold ecosystems together, much like the keystone in an arch.

KeystoneSpecies

A keystone and three keystone species. (A) This small keystone holds up an arch in the Shoenberg Temperate House at Missouri Botanical Garden. (B) Sea otters are keystone predators in kelp forests. Photo by Marshal Hedin CC-BY 2.0. (C) Gray Wolves are keystone terrestrial predators. Photo by Gary Kramer USFWS CC-BY-NC 2.0. (D) A keystone fig tree feeding a Knobbed Hornbill in Sulawesi, Indonesia. Photo by T. R. Shankar Raman CC BY-SA 3.0.

Plants can be keystone species too. Around the world there are about 800 species of fig trees, and they hold tropical forests together by providing food for a wide array of animals. On any given day, the busiest tree in a rain forest is likely to be a fig tree with fruits. Monkeys, birds, bats, and others gather at fig trees to eat, and in the process, they deposit seeds of other plant species that they have been carrying in their guts. This chain of events, repeated day after day, often turns the area beneath a fig tree into a hotspot of plant diversity.

A few years ago, we had an idea to plant keystone fig trees in young forests in Costa Rica. We wanted the figs to grow as fast as they could, so instead of planting seedlings, we planted cuttings – big ones. With help from our local collaborator, Juan Abel Rosales, we cut dozens of twelve foot-long branches from eight species of fig trees. We stripped off all of their leaves to keep them from drying out, and then we planted our figs trees in shallow holes.

FicWhat

Rakan Zahawi (delighted!) poses with a three year-old fig stake.

To our delight, many of the fig trees grew!

The ones that did the best came from a special group, the subgenus Urostigma. Many figs in this group have a unique life strategy. They begin their lives in the top of a tree when their tiny seeds are deposited on a branch by a bird or some other animal. As they grow in the treetop, they send long roots down to the ground, and these roots harden and fuse together, forming a lattice-like trunk. Over time, these figs kill their host trees by taking most of the water, nutrients, and light. They also keep the host tree from growing outwards, giving them the nickname “strangler figs”. Maybe the ability to transform a flimsy, dangling root into a solid trunk is related to these figs being able to grow from cuttings.

To find out how well our planted fig cuttings might survive over the long-term, we also tracked down some fig cuttings that we had planted in 2004. We were happy to learn that out of the trees that survived for their first three years of life, all of them were still thriving a decade later.

Full disclosure: planting large cuttings is not a new idea.  Farmers in many parts of the tropics plant trees this way to create ‘living fences’ – with all of the normal fixings like gates and barbed wire, but with a row of living trees instead of dead posts. The advantages for farmers are many – their fences don’t rot and fall apart (that happens quickly in the tropics); the trees provide shade for cattle; they have a constant source of new fence posts (by cutting off a limb); and in some cases they can feed the young shoots to livestock.

Big cuttings have big benefits for restoration too. Not only are planted trees already several feet tall, you also get to skip the pricey nursery phase, and, most excitingly, cuttings have a tendency to fruit quickly.

Some of our young fig trees are now making fruit, but we will have to wait a bit longer to see whether they start attracting more big animals and whether those animals carry more tree seeds into our young forests. For now, we can say that others who are interested in growing keystone figs for forest restoration may have the best luck by working with the stranglers.

For more information, please take a look at our open access paper on this project in Perspectives in Ecology and Conservation and prior blog posts here, here, and here.

FigProduction

How to grow an instant fig tree. (A) Remove a long, thin branch segment from an adult tree. The red arrow shows a cut branch. (B) Strip the cuttings of their leaves to keep them from drying out, then carefully transport cuttings so as not to damage cortical tissue. Here, cuttings are padded by a foam mattress. (C) Remove the bark from a ring on the cutting to promote root growth. Here, a ring is being cut about 20 cm (8 in) above the base so that it will be just below the soil surface when planted. (D) Dig a shallow hole and plant the cutting. Be sure that the cutting is firmly planted to prevent it from toppling, but take care not to compact the soil too much around its roots. Photos by Rakan Zahawi.

 

Seedlings planted for Brazilian forest restoration are not representative of tropical tree biodiversity

A collaborative research project involving MBG’s Center for Conservation and Sustainable Development, the Tropical Silviculture Lab at the University of São Paulo, and the PARTNERS research coordination network highlights important differences between the native tree flora of the Brazilian Atlantic Forest and the species that are widely planted for ecological restoration projects.

The Brazilian Atlantic Forest is a global biodiversity hotspot. This designation denotes two things. First, the Atlantic Forest is exceptionally and uniquely biodiverse. Second, the biodiversity of the Atlantic Forest is exceptionally threatened. This once-vast biome historically stretched from northern Argentina to Brazil’s eastern tip in Rio Grande do Norte, but it is now reduced to about 12% of its original size, and most of what remains exists as small, isolated fragments.

During the past decade, a major, multilateral effort has been undertaken to staunch biodiversity loss by doubling the size of the Atlantic Forest through ecological restoration. The Atlantic Forest Restoration Pact is composed of more than 270 private companies, governments, NGOs, and research organizations. It aims to restore 15 million hectares of Atlantic Forest by 2050.

Image_Atlantic_Forest_WWF

The Atlantic Forest biome: a global biodiversity hotspot and the site of the most ambitious tropical forest restoration project on the planet. Map imagery from NASA via Wikimedia Commons.

Atlantic Forest restoration projects are characteristically thorough and well-documented. For example, they often include high diversity plantings more than 80 tree species. Yet until recently there had never been a systematic study to evaluate how well these restoration plantings represented the Atlantic Forest biodiversity they aimed to protect.

Dr. Pedro Brancalion is a professor at the University of São Paulo’s agricultural school in Piracicaba, Brazil, where he co-directs the Tropical Silviculture Lab. Five years ago, he approached me at a meeting of the Society for Ecological Restoration in Madison, Wisconsin, and over a beer he told me about a dataset that he thought could shed light on the how well Atlantic Forest restoration projects were conserving tree biodiversity. The dataset consisted of seedling donation records from the NGO SOS Mata Atlântica. Between 2002 and 2015, the NGO donated more than 14 million tree seedlings to 961 restoration projects. By comparing the species composition in these records to tree species living in mature forests, we could see what elements of biodiversity might be missing and how this could be affecting carbon stocking – an important factor in mitigating global climate change.

Even in high diversity plantings, many of the most threatened tree species were not included.

Last month, Pedro and our collaborative team published a paper in Conservation Letters describing our results. We found that restoration projects in the Atlantic Forest biome had included 416 tree species out of the >2,500 tree species known from mature and old-growth forest fragments. This is an impressive figure, but the team discovered that it reflects a highly biased subsample of the Atlantic Forest tree flora. The most under-represented species were those with large seeds that are dispersed by animals. Animal-dispersed trees make up as much as 89% of tree species in some parts of the Atlantic Forest and include some of the most threatened species.

The reason that large-seeded, animal-dispersed species are being used less often was probably related to the cost and challenges of collecting and growing seeds. Large-seeded, animal-dispersed trees are more expensive to purchase from nurseries than small-seeded or wind-dispersed species. Because they are energetically expensive to produce and are contained within large fruits, trees tend to produce large seeds in relatively low quantities, with just one or a few seeds per fruit. They are generally found in remote forest areas, and seed collectors have to compete for them with seed-eating animals, like peccaries and agoutis. Once large seeds are collected, they also take up considerably more space in storage and production facilities.

Image_SeedComparison

In our analysis of animal-dispersed tree species, seed diameter explained 87% of the variance in seed price. Large seeds like those of Caryocar brasiliense were much more expensive than small ones, like Ficus guaranitica. Grid size: 1 mm. Photos reproduced from C. N. Souza Junior & P. H. S. Brancalion (2016).

The absence of large-seeded, animal-dispersed tree species in restoration plantings has important implications for biodiversity conservation. First, fewer large-seeded trees means less food for large birds, some of which eat mainly large fruits. Second, these species are sometimes overharvested for timber and have difficulty recolonizing forests from which they have been removed. So the fact that large-seeded, animal-dispersed trees are under-represented in restoration projects means that even if the ambitious restoration goals of the Atlantic Forest Restoration Pact are met, the increase in forest cover may not improve dispersal between fragmented populations of the most vulnerable species.

Large-seeded tree species also tend to store carbon more densely than small-seeded species. This tendency is related to large-seeded species growing slowly in the shady understory of the Atlantic Forest and their gradual formation of dense wood, which is rich in carbon. We simulated potential carbon stocking in restored forests and compared it to mature forests, and our results showed that under-representation of large-seeded, animal-dispersed trees could cause a 2.8-10.6% reduction in carbon storage. Based on the current price of carbon, this loss could represent $17-63 USD per hectare in lost carbon credits.

Fragment_Pedro

Many Atlantic Forest restoration projects are quite isolated. A large seed would have a hard time reaching sites like this forest in a sugarcane matrix. Photo by Pedro Brancalion.

Reduced capacity for biodiversity conservation and carbon stocking sounds like bad news, and indeed it is not ideal. However, restoration ecology moves forward by identifying problems and seeking scientifically-based solutions to overcome them. Knowing that large-seeded, animal-dispersed trees are under-represented in restoration plantings means that we can turn our attention to innovative solutions.

For example, new policies could help bridge the gap between Brazil’s exceptional tree biodiversity and the relative paucity of species being used for ecological restoration. One way this could happen would be for the Brazilian government to subsidize the cost of producing large-seeded, animal-dispersed tree seedlings. This could be done through financial incentives or potentially by opening some forest reserves for seed harvesting, to make it easier for collectors to acquire these species. Facilitating uptake by reducing costs would be a carrot. A stick could be to legally mandate some representation of these species in future restoration plantings.

Market solutions may also exist. Based on our calculations, adding more large-seeded, animal-dispersed species to restoration plantings would increase carbon storage and carbon credits, offsetting the cost of the expensive seedlings and creating a net gain of $3-32 USD per hectare.

Banner image: Sterculia striata (Malvaceae). Photo by Mauricio Mercadante. CC BY-NC-SA 2.0.

Drivers of epiphyte recovery in secondary forests in southeastern Brazil

Alex Fernando Mendes is an undergraduate researcher in the Tropical Silviculture Lab at the University of São Paulo, Brazil. He describes his thesis project, undertaken in dozens of forest fragments in the endangered Atlantic Forest biome. Currently, Alex is analyzing his data as a visiting researcher in the Center for Conservation and Sustainable Development.

Historically, intensive agriculture in the Brazilian Atlantic Forest has caused large-scale deforestation of this biome. However, new legal requirements, land exhaustion, and the shifting priorities of farmers have recently allowed forests to regenerate on some formerly farmed lands. Given the unique nature of the Atlantic Forest, its high species endemism, and its potential for providing ecosystem services, the Tropical Silviculture Lab (LASTROP) at the University of São Paulo, coordinated by Prof. Pedro Brancalion and its partners, initiated a project in 2014 to better understand the structure and composition of these new forests.

However, forests aren’t made solely of trees. Among the plant components of a forest, there are others life forms such as epiphytes, lianas, and herbs that contribute to biodiversity and provide food, water, and shelter for many animal species. Epiphytes are plants that use other plants as support. Due to their sensitivity to environmental changes, epiphytes can be used as bioindicators. Therefore, we asked how these plants are doing in these young regenerating forests. And what landscape and local attributes facilitate or hinder their recolonization?

image1.jpg

Epiphyte species found in second-growth forests of the Atlantic Forest – A) Philodendron bipinnatifidum Schott; B) Lepismium houlletianum (Lem.) Barthlott.; C) Ionopsis utricularioides (Sw.) Lindl.; D) Catasetum fimbriatum (E. Morren) Lindl. & Paxton; E) Aechmea bromeliifolia (Rudge) Baker; F) Billbergia sp.

 

To try to answer these questions, we are studying the epiphyte communities in 40 second-growth forests (i.e., forests that were once completely cut down). We are considering three landscape drivers (distance from watercourses, distance from forest edge and forest cover in a 1-km buffer around the remnant) and four local drivers (previous land use, forest age, liana abundance, and tree basal area). We expect that forests close to watercourses would provide the moisture required by epiphytes. We expect to find more epiphytes further from the forest edge since forest cover in more conserved forests may limit their establishment. Since our forests regenerated from abandoned eucalyptus plantation and pastures, we want to check if the non-native eucalyptus could act as a filter preventing epiphytes recolonization. We also expect that older forests and forests with more basal area could house more epiphytes than young forests. Finally, field observations made us wonder if lianas could compete with epiphytes by occupying the same niche.

Of the more than 6,000 phorophytes (trees that could support epiphytes) sampled in these 40 forests we found 398 epiphytes belonging to 21 morphospecies distributed in 4 families (Araceae – 1 species, Bromeliaceae – 14 species, Cactaceae – 5 species, Orchidaceae – 5 species). Only three species, Tillandsia pohliana, Tillandsia tricholepis, and Ionopsis utricularioides, represented more than half (59.5%) of all epiphytes found in second-growth forests. The genus Tillandsia was expected to be abundant in these young forests, since these are disturbance-adapted species that can even be found growing on power lines in cities.

Image2

Epiphytes of the genus Tillandsia (Bromeliaceae) are often found in extreme microenvironments in urban areas (Photos by A. Mendes, 2017).

Our analysis is in progress, but our preliminary observations suggest that forests closer to watercourses and closer to forest edge are more likely to have epiphyte recolonization than forests far from edge and watercourses. Forests regenerated on pastures have more epiphytes than those on abandoned eucalyptus plantation. Our dataset will soon be upgraded with new forest types: conserved and disturbed old-growth forests, and mixed tree plantings for forest restoration, totaling approximately 70 forests with epiphyte samples.

With this research, we hope to find out the local and landscape factors that contribute to epiphyte recolonization in second-growth forests. In practice, this will allow us to locate sites with limited potential for spontaneous colonization of this life form to take actions that promote colonization and establishment, such as introducing individuals. Finally, by identifying epiphytes species that are more sensitive to disturbance, we can focus our reintroduction interventions.

Landscape

Small, remnant forests are surrounded by cattle pastures in southern Brazil.

Note: The image of Philodendron bipinnatifidum featured at the top of this post was taken by David Stang. 

Tree islands for tropical forest restoration: the outlook is rosy after 10 years

Planting tree islands has many of the benefits of larger plantations, but entails significantly less cost. Karen Holl (University of California, Santa Cruz), Leighton Reid (Missouri Botanical Garden), and Zak Zahawi (American University of Beirut) describe recent findings on tree seedling recruitment in a long-term experiment in southern Costa Rica.

Over the past few years there have been a growing number of commitments at the global, national and regional scale to restore forests because of their importance to conserve biodiversity, sequester carbon, reduce erosion, and provide goods and services to people. For example, Initiative 20×20, led by the International Union for the Conservation of Nature, aims to restore 20 million hectares of tropical forest by 2020, an area roughly equivalent to the size of Uruguay or Nebraska.

A common strategy to restore forests is to plant trees. But, the big question is: where will the money come from to plant billions of trees when there are so many pressing needs? As restoration ecologists, we started thinking about how we could most efficiently allocate resources to get the best bang for the buck and restore the largest area of forest.

expdesignnher

Trade-offs in forest restoration strategies. Planting fewer trees leaves more to chance and can require more time, but tree plantations are more expensive and leave a bigger ecological footprint. Our study tests an intermediate option, and after 10 years it appears to provide a good balance. Figure modified from Corbin & Holl (2012).

Starting over 10 years ago, we set up a large-scale tropical forest restoration experiment in southern Costa Rica to test two ideas.

First, we tried planting tree “islands”. The idea is to plant groups of trees that attract birds and bats, which disperse most tropical forest tree seeds. The tree canopy also shades out light-demanding grasses that can outcompete tree seedlings. In one experimental treatment, we planted tree islands that covered about 20% of 50 × 50 m plot of former cattle pasture. We compared that to plots where no trees were planted (natural recovery) and to the more intensive (and more typical) restoration strategy of planting trees in rows throughout the plot (plantation).

Second, we asked: is it only possible to restore forest near remnant forests or can you restore forest anywhere in the landscape? This is important information to help guide forest restoration efforts. To do this we set up our entire experiment at 13 sites, some of which were mostly surrounded by agricultural land and some of which were adjacent to the largest remaining forests in the region.

Then we monitored establishment of new tree seedlings in our research plots over a decade. We compared the number of seedlings, number of species, and types of species in the restoration plots with those found in the nearby forest to evaluate how well the forest is recovering.

The tree island planting method not only saves money on buying, planting, and maintaining seedlings, but it also results in a more heterogeneous distribution of trees, so it looks more like a natural forest.

om-i3

Profuse tree seedling and sapling recruitment in the understory between two tree islands in southern Costa Rica.

We counted over 6000 tree seedlings, 88% of which have seeds that are dispersed by animals. On average there were many more tree seedlings in the tree island and plantation treatments than in the natural recovery plots. These results suggests that some tree planting helps the forest to recover faster, but that it is not necessary to plant the whole area with trees. The tree island planting method not only saves money on buying, planting, and maintaining seedlings, but it also results in a more heterogeneous distribution of trees, so it looks more like a natural forest.

Even though there were many tree seedlings in the island and plantation plots, on average there were less seedlings of tree species that have big seeds (>0.5 cm/0.2 inches across) compared to mature, reference forests. It seems that the larger-seeded species that are common in mature forests are much slower to colonize restored sites, likely because they are eaten and dispersed by a small number of larger animals, such trogons and agoutis. Many of those dispersers are less likely to visit early successional forest.

wheelwright_nher

Small frugivores, small seeds. Most of the birds we see in these experimental plots are small-gaped omnivores (e.g., Yellow-bellied Elaenia, Elaenia flavogaster, left), but it usually takes large-gaped species to disperse larger seeds1. The figure at right shows the maximum fruit size that a bird species with a given gape size was able to consume in a cloud forest in central Costa Rica (modified from Wheelwright (1985)). In our experiment, small seeds were ubiquitous, but large seeds were mostly absent.

We were surprised that the amount of forest cover around the experimental plots had a weak effect on the number of seedlings establishing. In other words, isolated plots had just as many tree seedlings as plots right next to old-growth forests. We think that this is likely due to the fact that there are many trees in the agricultural landscape surrounding our plots; these trees include remnant trees, living fence rows, and riparian corridors. Trees in the landscape can serve an important role in both providing sources of seeds and stepping stones for the movement of seed-dispersing fauna. We anticipate that having forest nearby will be more important in future years as these forests build up greater diversity of rare, large-seeded species. Nonetheless, our results suggest that there are good prospects for restoring forests in many locations in this landscape.

Our key finding is that planting tree islands can be a cost-effective way to restore tropical forests at our study site in Costa Rica, but we hasten to note that the strategy should be tested in other locations, particularly areas with fewer forest elements in the surrounding countryside. Our study also demonstrates that tropical forests can recover some species quickly but it will take many decades, if ever, for forests to fully recover. So, preserving existing rain forests is critical to conserve biodiversity and the services they provide to people.

landscape

Diverse tree cover in an agricultural landscape in southern Costa Rica. Remnant trees in pastures, trees along fence rows, and riparian forests provide important sources of flora and fauna to speed up forest recovery.

1See Melo et al. (2009) for an example to the contrary: small-gaped animals dispersing fairly large fruits and seeds.

This work was supported by a grant from the National Science Foundation.

Ecological Restoration in a Changing Biosphere

If you were at the MBG Fall Symposium, we want to hear from you! How did the symposium change your perception of restoration? Send us an email at leighton.reid@mobot.org.

On October 8th, Missouri Botanical Garden hosted its 63rd annual Fall Symposium. This year’s theme was Ecological Restoration in a Changing Biosphere. Author and journalist Paddy Woodworth moderated the day, and seven speakers presented contemporary perspectives on a core challenge in modern restoration ecology. Namely: in the post-COP21 world, when all three UN conventions call for scaling up and mainstreaming of restoration, it is clear that restoration will affect hundreds of millions of hectares – and as many people – over the coming decade. At the same time, we find ourselves in an era of unprecedented change where climate, ecological baselines, and future land-use changes are highly uncertain. This raises the question: What should large-scale restoration look like in the remainder of the 21st century?

symposium_group-photo_01

2016 Fall Symposium speakers. From left to right: Peter Wyse Jackson, Curt Meine, Robin Chazdon, James Aronson, Leighton Reid, Pedro Brancalion, Karen Holl, Don Falk, Paddy Woodworth, and Jim Miller. Photo by Andrea Androuais.

Talks during the morning focused on tropical forests, where much of the international restoration dialogue is focused.

  • Leighton Reid (Missouri Botanical Garden) opened with a presentation on restoration longevity – the idea that some restoration projects create ecosystems that persist for more than a century (e.g., Floresta da Tijuca), while other projects fail quickly. Dr. Reid argued that how long restored ecosystems persist is quantifiable, predictable, and manipulable, opening the possibility for more ambitious restoration planning.
  • Robin Chazdon (University of Connecticut and beyond) then spoke about forest landscape restoration, an approach that aims to regain ecological integrity and enhance human well-being in deforested, human-impacted, or degraded forest landscapes. Drawing on a wealth of large-scale studies, Dr. Chazdon made the case that natural forest regeneration is the most ecologically effective and economically feasible approach to forest restoration globally.
  • Karen Holl (University of California Santa Cruz) presented her take on research priorities for forest restoration in the Neotropics. She highlighted that researchers could make an impact by studying forest restoration at larger spatial scales, at longer temporal scales, and in collaboration with stakeholders. Improving information exchange and standardizing monitoring protocols were also among her top priorities. (Graduate students, take note!)
  • Dr. Pedro Brancalion (University of São Paulo) completed the morning session with a TED talk-style discussion of the linkages between science, technology, policy, and best practice in Brazilian Atlantic Forest restoration. Using Thomas Kuhn’s structure of scientific revolutions, Dr. Brancalion argued that restoration ecology is in a crisis period, in part because disciplinary research has predominantly created solutions at smaller spatial scales than the (growing) problems the discipline seeks to address. Perhaps restoration is ripe for a paradigm shift?
rc_pedro

Dr. Pedro Brancalion (right) asks whether restoration ecology is ready for a new paradigm shift, as Paddy Woodworth (left) moderates. Photo by Robin Chazdon.

After lunch, the conversation turned towards a major academic debate in restoration ecology. Has global change outpaced the restoration approach? And is a new approach needed?

  • Curt Meine (The Aldo Leopold Foundation) drew on his long experience in the upper Midwest, and, in particular, his studies of author and environmentalist Aldo Leopold (1887-1948). He argued that Leopold avoided the simple polarities through which some contemporary restoration debates are framed. He viewed nature in a relative way, neither entirely wild, nor entirely domesticated in any given landscape. Although he practiced ecological restoration in some contexts, he also advocated soil conservation and sustainable agriculture – activities motivated by his core values, as expressed in The Land Ethic (1949).
  • James Aronson (Missouri Botanical Garden) followed with an elucidation of the reference ecosystem concept. Reference ecosystems, he noted, help determine the social and ecological vision for a restoration project or program – a critical issue for restoring historic continuity in degraded landscapes. Dr. Aronson described a family of restorative actions for achieving progress towards the reference system, drawing on examples from Jordan and South Africa. He argued we need to look deeper into the past and ponder our choices from many angles as we decide how to do more effective restoration at the landscape and larger scales.
  • Donald Falk (University of Arizona) delivered the keynote address. He painted a disturbing portrait: rapid climate change is driving a massive forest-to-non-forest transition in the southwestern United States. In particular, many ponderosa pine forests will not be able to persist in the future where they have been in the recent past and present. Perhaps restoration ecologists should transition too. Rather than “chasing the ambulance”, maybe we could get out ahead of disasters and ease transitions between stable ecosystem states. Anticipating ecosystem transitions could mitigate the loss of ecosystem functioning that accompanies major climate-driven forest fires, but it would require a shift in restoration thinking. Importantly, Dr. Falk noted that ecosystems do not care what words we use – ecosystems respond to actions.

With moderator Paddy Woodworth’s help, we finished the day with a panel discussion, inviting questions from the audience. Among the thoughts and questions that we were left with:

  • Is ecological restoration more difficult in places with greater population density?
  • Should restoration focus on policy, economic, or cultural motivations for engaging people?
  • Are values a better guide for land management than ecological history? Are the two complementary?
  • How can the reference ecosystem concept accommodate rapid biome changes, as we are seeing in the Southwestern USA?
  • What is the way forward to mainstream serious, multisectorial monitoring and evaluation with all these new factors to consider? Who will fund it?
  • To what extent can we move from restoring degraded ecosystems to avoiding degradation in the first place?
  • Can forest landscape restoration and natural forest regeneration bridge the gap between small-scale, past restoration experience and present, large-scale restoration needs?
rc_lelandricardo

PhD candidates Ricardo Cesar (University of São Paulo) and Leland Werdan (University of Minnesota) compare notes on seedling functional traits in dry tropical forest restoration. Leland was the recipient of the annual Delzie Demaree award. Photo by Robin Chazdon.

mbg63-registrants

More than 150 people registered for the symposium. They came from three continents, five countries, and seven US states.