Planting trees recovers 70 years’ worth of dead wood carbon pools in less than two decades

By Estefania P. Fernandez Barrancos, a PhD candidate in Biology at the University of Missouri – St. Louis and a fellow of the Whitney R. Harris World Ecology Center. Her most recent research paper in Forest Ecology and Management is freely available through March 9th.

When most people walk through a forest the last thing they probably look at is dead vegetation, and unless you are an avid mushroom harvester you probably don’t even notice dead logs. However, dead wood stores an important amount of carbon. An amount important enough that if dead wood disappeared it could promote more changes to our already rapidly changing climate.

Mushrooms on a dead log. Photo: JL Reid.

Dead wood is also a crucial habitat for many organisms such as fungi, insects, and birds. Many insects and fungi use dead wood as a source of food and nutrients, and several species of birds are only able to nest in dead logs.

A Resplendent Quetzal (Pharomachrus mocinno) exiting its nest inside a standing dead log to go harvest food for its fledglings. Photo: Estefania Fernandez.

Anthropogenic disturbances, such as logging and deforestation, can significantly decrease the amounts of dead wood present on the forest floor, sometimes leading to losses of up to 98% of dead wood. The implications of dead wood loss are potentially warmer temperatures due to the release of carbon contained in dead wood as well as the loss of habitat that is critical to many forest organisms. Tropical ecosystems contain some of the most biodiverse habitats on Earth, yet they are among the ecosystems that suffer the most from anthropogenic disturbance. For example, most forests in the county of Coto Brus in Southern Costa Rica, our study area, were transformed into cattle pasture or coffee plantations in the 1950s-1980s. Today, the landscape consists of a mosaic of cattle pasture, coffee plantations, and small forest remnants.

Deforestation to create farms and cattle pastures has decreased the amount of dead wood in southern Costa Rica. Photo credit: JL Reid.

Forest restoration is the process of assisting the recovery of an ecosystem that has been damaged or destroyed (SER International Standards) and it has a high potential to reverse the problem of dead wood loss through different strategies. In the Tropics, the most common restoration strategies are passive and active restoration. Passive restoration consists of allowing an ecosystem to recover with minimal to no human input.  In contrast, active restoration consists of assisting the ecosystem in its recovery through actions such as tree planting.

Old-growth forest (A) and and two restoration treatments: tree plantations (B) and natural regeneration (C). Old-growth forests are ≥100 years old. Plantations and natural regeneration were 16-17 years old at the time of the study. Photos:  Juan Abel Rosales & Estefania Fernandez.

Recently, I studied the pattern of dead wood re-accumulation through time after disturbance in southern Costa Rica as well as the effectiveness of passive and active restoration at recovering dead wood as it is found in undisturbed forests. To evaluate dead wood accumulation through time, my team and I surveyed dead wood volumes inside 35 forest patches of increasing ages (from 3 to over 100 years old) that were former coffee plantations. We evaluated the effectiveness of active vs. passive restoration at recovering dead wood by surveying dead wood volumes inside 17-year old passive and active restoration plots and inside nearby old-growth forests. Our passive restoration treatment was represented by natural regeneration plots around which fences were established to exclude cattle and where vegetation was allowed to re-establish naturally. Our active restoration treatment was represented by restoration plantations, where seedlings of two native (Terminalia amazonia and Vochysia guatemalensis) and two naturalized (Inga edulis and Erythrina poeppegiana) tree species were planted 17 years ago to facilitate the re-establishment of vegetation. Our reference ecosystem included nearby old-growth forests over 100 years old.

Juan Abel Rosales measures the diameter of dead logs in order to estimate their volume in an old-growth forest in Southern Costa Rica. Photo: Estefania Fernandez.
To measure the diameter of dead, rotting logs, we measured the distance between two tent poles set vertically along the logs’ edges. Photo: Estefania Fernandez.
Jeisson Figueroa Sandí establishes a transect to evaluate dead wood inside a forest fragment. Photo: Estefania Fernandez.

We found that dead wood recovers following a logistic shape through time in our study area: volumes are low initially, increase rapidly, and then plateau. The low volumes of dead wood at the beginning of succession could be explained by the fact that most of the wood remains are typically harvested by local inhabitants after lands are abandoned in our study area. As pioneer trees recolonize abandoned coffee plantations and subsequently die, they produce dead wood. As the forest grows older, there is a mix of short-lived pioneer trees and long-lived trees which contribute to large amounts of dead wood on the forest floor through branchfall and their own deaths.

Dead wood volumes as function of forest age in a chronosequence of secondary forests in southern Costa Rica. Blue dots represent the raw data (i.e. course woody debris, or CWD, volumes per hectare). The red line represents the predicted values from a generalized linear model plotted using a smoothing function. Eight outliers that were included for the analysis where CWD volume per transect was ≥125 m3ha-1 were removed for better visualization. CWD volumes in plantations (purple dot), natural regeneration (yellow triangle) and five nearby old-growth forests (green dot) are also represented. Mean CWD volumes per hectare for each restoration plot (n=5) and corresponding 95% confidence intervals are shown.

We also found that restoration plantations contain 41% of dead wood amounts found in old-growth forests, whereas natural regeneration only contained 1.7% of dead wood volumes found in old-growth forests. The extremely low recovery of dead wood in natural regeneration might be explained by the fact that our natural regeneration plots were dominated by exotic grasses which typically hamper tree colonization. If there are no trees growing in the plots, there cannot be dead wood either. This is an important finding, because it shows that restoration plantations area a faster and more efficient way to recover dead wood in this fragmented, pasture-dominated landscape, even though this restoration strategy might be more time consuming and expensive due to the costs and time of planting seedlings.

Overall, our study unveils an important forest process, showing that dead wood carbon pools recover following a dynamic logistic pattern through time in this Neotropical forest region. Knowing that dead wood is 50% carbon, our findings allow us to predict carbon stocks in Neotropical forests more accurately. Our study also shows that restoration plantations accelerate the recovery of dead wood carbon pools in this Neotropical ecosystem, and potentially promote the preservation of dead wood-associated biodiversity.

For more information, see our recent paper in Forest Ecology and Management, which is freely available online through March 8th, 2022.

30 dump truck loads of coffee pulp help restore a Costa Rican rainforest

Rakan “Zak” Zahawi is the executive director of the Charles Darwin Foundation in Galápagos, Ecuador. He and his collaborator, Rebecca Cole, partnered with a coffee processing plant to repurpose farm waste and help restore a rainforest. Read more about the project in an open access article in Ecological Solutions and Evidence.

From the very first time I saw the results of the orange peel project on the ground back in 2004 I was sold! What a brilliant idea I thought – use the waste products generated from the production of orange juice (and any related citrus products) to regenerate degraded habitats where expansive dry forests were once found. The idea was Dan Janzen’s, an ecologist at the University of Pennsylvania who has worked in northern Costa Rica for the better part of 50 years. At the time I was working for the Organization for Tropical Studies (OTS) and given that I work as an ecologist in forest restoration, a colleague thought I might be interested.

One of thirty dump truck loads of coffee pulp, locally called brosa, spread on former farmland to restore rainforest in southern Costa Rica. Photo credit: Rebecca Cole.

The idea is simple, take truckloads of agricultural waste (in this case orange peels) and spread them in a layer ~0.5 m thick across hectares of extremely degraded land dominated by forage grasses. Under the tropical sun this layer generates an enormous amount of heat, and in the process of ‘cooking’ down it asphyxiates and kills the forage grass that is notoriously difficult to eradicate. At the same time, birds and other seed dispersers visit the site, attracted by the abundant larvae helping to decompose the material. The net result is a lot of organic material and nutrients and many seeds dispersed combining to help jump-start the recovery of a degraded habitat and return it to a forested state.

I never forgot that visit and over the years that I worked in southern Costa Rica as Director of the Las Cruces Biological Station (a field station run by OTS) I always thought of trying the study there. The difference was that there was no orange production in the region but another agricultural byproduct was widely available – coffee pulp waste! I wondered – could the results of the orange project be replicated with another agricultural waste product? While the idea was always on my mind, it took more than a decade for me to actually test it after Rebecca Cole, a long-term research colleague who was based at the University of Hawaii expressed interest in collaborating.

Before: a former cattle pasture in southern Costa Rica. Photo credit: Rebecca Cole.
During: coffee pulp piled half a meter high over the experimental plot. Photo credit: Rebecca Cole.
After: the area piled high with coffee pulp rapidly grew into a secondary forest (left) while the control area remained covered in pasture grass, as it has been for decades (right). Photo credit: Rebecca Cole.

With funds secured from the March Conservation Fund, we setup a modest pilot study with a 35 × 45 m plot buried half a meter deep. That’s 30 dump trucks – or 360 m3 of material! As with the orange peel study, this land was primarily degraded pasture and would have been slow to recover on its own. We monitored this and an adjacent similar-sized plot for 2 years and the results were nothing short of spectacular. While the control treatment languished with overgrown grasses with a few shrubs, the coffee waste plot was completely transformed. The grass was smothered and in its place a patch of young trees. All species were pioneers but they are nonetheless critical to the recovery process – and the fact that they dominated the entire plot was really promising. With time it is hoped that more mature forest species will come into this system and establish – and with a young canopy of pioneers providing a little shade, the conditions are perfect for this to happen!

Drone image showing the area where coffee pulp was dumped (left) and the control plot (right) after two years. Photo credit: Rakan Zahawi.

This study is a small pilot project, but the results speak for themselves. So does the coffee industry! Every year, millions of tons of coffee pulp waste are generated and finding a way to not only dispose of this waste in an ecologically sound manner, but also use it for habitat recovery is a win-win for everybody. It is exceedingly rare for industry to be able to pair up so seamlessly with conservation and restoration that it is hard to believe. Of course, there are hurdles – such as governmental regulations that manage such waste products, but the potential here is enormous.  And the next challenge before us is to see if we can bring this idea to scale and test the methodology across big areas of degraded habitat in the tropics. We will keep you posted!

Read more about this project in a recent open-access article published in Ecological Solutions and Evidence.

Drought, flood, and fire: an unexpected habitat recipe for at-risk bats

Mike Saxton is an ecologist restoration specialist at Shaw Nature Reserve, a 10 km2 mosaic of restored and reconstructed woodlands, prairies, wetlands, and riparian forest along the Meramec River in Gray Summit, Missouri.

For most land managers, there aren’t enough hours in the day. Between invasive species management, native seed collection and prescribed fire implementation, there are never enough boots on the ground. Add in equipment break downs, erratic weather and administrative tasks and it’s no surprise that with so many balls in the air, something gets dropped. Far too often, we drop the ball on science and monitoring, which are critically important for biodiversity-driven ecosystem management and restoration. Research and monitoring can, in some cases, be expensive; usually they take a certain amount of specialization, and they most certainly take time. For these reasons and many others, land managers build partnerships with universities, collaborate with outside agencies, and engage the public in community science to meet research and monitoring needs.

What follows is an example of a highly successful partnership between non-profit organizations, a private consulting group, and a federal agency to better understand and protect a federally endangered species.

A female Indiana bat, “Celeste”, captured during mist netting surveys at Shaw Nature Reserve in 2017 and 2019. Photo credit: Cassidy Moody.

In 2017, Shaw Nature Reserve hosted a Bioblitz partnering with the non-profit Academy of Science, St. Louis. For two days, participants combed the area looking for as many plant and animal species as they could find. A single federally endangered Indiana bat (Myotis sodalis) was captured during an evening mist netting session along a riparian corridor, marking the first time this species was documented at the Nature Reserve.

Wildheart Ecology, the local consulting firm which carried out the Bioblitz bat survey, returned in the summer of 2018 to deploy acoustic detectors to further document bat populations at the Nature Reserve. The data revealed the presence of nine different species, including the Indiana bat, the endangered gray bat (Myotis grisescens), and several other species of conservation concern.

The audio signature of an Indiana bat, captured by detectors at Shaw Nature Reserve. Courtesy: Wildheart Ecology.

After these surprising and impressive findings, scientists at the U.S. Fish and Wildlife Service carried out mist netting in summer 2019 at the Nature Reserve to gather more information about the federally endangered population of Indiana bats. Netted individuals were tagged and fitted with tiny transponders. Using telemetry, USFWS staff were able to locate a maternal roost colony tree in the Meramec River flood plain. After multiple emergence sampling events conducted at dusk, the population is estimated to be 150+ individuals, making it one of the largest recorded in Missouri.

Indiana bat roost site at Shaw Nature Reserve. Photo credit: Cassidy Moody.

So how did Shaw Nature Reserve end up with one of the state’s largest populations of at-risk bat species? The story begins in fall 2015, when a major flooding event on the Meramec River deposited large amounts of woody biomass and created logjams in the Nature Reserve’s floodplain. Another major flooding event in the spring 2017 compounded these conditions. In the fall of 2017, moderate drought gripped the region, drying leaf litter and woody fuels on the forest floor. In November of that year and on a low humidity day in drought conditions, we conducted a prescribed fire that thoroughly burned the floodplain forest, which normally does not carry fire. The flames crept into flood-debris logjams, causing a major conflagration. Dozens of floodplain forest trees died — mostly silver maple, elm and cottonwood— leaving an open patch of larger-diameter snags, or upright dead trees. It is in these snags where the federally-endangered Indiana bats have found a home. Turns out, the serendipitous convergence of flood, drought, and fire created just the ideal conditions. Couple that with high-quality foraging areas across a healthy, diverse, managed landscape and this population is thriving.

Indiana bat roost habitat along the Meramec River at Shaw Nature Reserve in Gray Summit, Missouri. Photo credit: Cassidy Moody.

Current status of Indiana Bats

Unfortunately, like many bat species, the Indiana bat has been in decline and imperiled by human disturbance and disease. According to the U.S. Fish and Wildlife Service, hibernating Indiana bats are especially vulnerable to disturbance, since they often congregate in large numbers – from 20,000 to 50,000 – to overwinter. A large number of deaths can occur if humans disturb these caves during hibernation. While other factors are also responsible for their decline, the devastating wildlife disease known as white-nose syndrome — discovered in 2006 — is a serious threat to the long-term survival of the species.

According to the U.S. Fish and Wildlife Service population status update, the states with largest net loss of Indiana Bats since 2007 (% decline since 2007) includes:

1. Indiana: -53,220 (-22%)
2. New York: -39,367 (-75%)
3. Missouri: -18,157 (-9%)
4. Kentucky: -15,220 (-21%)
5. West Virginia: -14,125 (-96%)
6. Tennessee -6,509 (-73%)
7. Ohio: -4,739 (-62%)
8. Pennsylvania: -1,027 (-99%)

What Can Be Done

With thoughtful management and strategic planning, conservation practitioners can conserve and restore bat habitat. Providing a continuous supply of roosting trees and maintaining a habitat structure to facilitate foraging are key aspects of restoration and management plans for bats. According to the Beneficial Forest Management Practices for White Nose Syndrome-affected Bats, below are some best-practice guidelines for achieving these goals:

  • Harvest timber during the hibernation period to eliminate or significantly reduces the likelihood of direct fatality or injury to tree-roosting bats.
  • Create large-diameter snags and canopy gaps, via girdling or chemical (e.g., “hack and squirt”) methods, to increase sun exposure to existing and potential roost trees.
  • Increasing midstory openness to facilitate travel corridors and foraging opportunities via increased mobility and insect prey detection.
  • Retain or create large-diameter snags during forest regeneration harvests or when managing stands affected by windthrow or disease/insect outbreaks.
  • Limit aerial or broadcast spraying near known hibernacula, maternity sites, and surface karst features, unless it can be demonstrated that it would have no adverse impact on bat populations or habitat.
  • Avoid disturbances near maternal roost sites or colonies when possible.
  • Fell hazard trees that appear to provide bat roosting habitat and do not pose an imminent danger to human safety or property during winter (hibernation period) and avoid removing them during June and July when non-flying bat pups may be present.
  • Avoid burning during cold periods since this can be detrimental to colonies of some species if individuals cannot escape smoke and heat from fires.
  • Apply low-intensity fires when possible since high-intensity fires are more likely to cause injury.
  • Account for caves, mines, important rock features, bridges, and other artificial structures when developing burn plans since these locations are often occupied by roosting or hibernating bats.
  • Remove hazard trees and construct fire-lines during winter, when possible, to reduce chances of removing occupied roost trees or disturbing maternity colonies.
  • Protect known maternity roost trees and exceptionally high-quality potential roost trees (e.g., large snags or large-diameter live trees with lots of exfoliating bark) from fire by removing fuels from around their base prior to ignition.
  • Limit management activities and disturbances near cave entrances.
  • Eradicate and control invasive plants to improve habitat quality for bats.

Do we really need to plant a trillion trees? Tree islands are an ecologically and economically sound strategy to facilitate tropical forest recovery

Karen Holl (UC Santa Cruz) and Leighton Reid (Virginia Tech) describe lessons learned from a 15-year study of tropical forest restoration in southern Costa Rica. Their new paper is published in the Journal of Applied Ecology.

It seems that everybody from business people to politicians to even Youtubers is proposing that we should plant millions, billions, or even trillions of trees. They cite a host of reasons, such as storing carbon, conserving biodiversity, and providing income. These efforts should be done carefully and with a long-term commitment to ensure that the trees survive and to prevent unintended negative consequences, such as destroying native grasslands, reducing water supply in arid areas, or diverting attention from efforts to reduce greenhouse gas emissions.

Another important question is whether we really need to plant that many trees to restore forest. In a new paper in the Journal of Applied Ecology, we summarize some the lessons we have learned about a different approach.

Volunteer plants tree seedlings in one of our plantations in southern Costa Rica. Photo: Karen Holl

Over 15 years ago, we set up an experiment in southern Costa Rica to test whether planting small patches or “islands” of trees could speed up forest recovery for a lower cost than typical tree plantations. The idea is to plant small 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. As a result, over time these tree islands spread as they grow and facilitate the establishment of a lot more trees.

Compared to tree plantations, the tree island approach has two major benefits. First, it better simulates the patchiness of natural forest recovery. Second, it costs much less than planting rows and rows of trees.

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 15 years it appears to provide a good balance. Figure modified from Corbin & Holl (2012).

In our experiment, we planted tree islands that covered about 20% of a 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). We repeated this set-up at 15 sites in 2004-2006.

Over the past 15 years, we have monitored the recovery of vegetation, litterfall, nutrient cycling, epiphytes, birds, bats, arthropods, and more. Our data reveal a few key lessons about how to restore tropical forests more ecologically and economically.

First, our data show that planting tree islands is as effective as bigger tree plantations, despite cutting costs by around two-thirds. Compared to plantations, tree islands have similar recovery of nutrient cycling, tree seedling recruitment, and visitation by fruit-eating animals. Both tree islands and plantations speed up tropical forest recovery compared to letting the forest recover on its own. After 15 years, cover of trees and shrubs in the island planting plots has increased from 20% to over 90%.

Artist's depiction of three tropical forest restoration treatments: natural regeneration, tree islands, and plantation.
Drawing of our three treatments showing a few trees establishing in the natural regeneration plots, the tree island merging canopies merging in the island plots, and the rows of trees in the plantation. Artist: Michelle Pastor.

Second, we have found that larger tree islands are more effective than smaller islands in enhancing the establishment of fauna and flora, as larger tree islands attract more birds and shade out competitive grasses.

Third, while tree islands cost less than plantations, some landowners won’t use the tree island approach because the land looks “messier” than orderly tree plantations. Some people prefer to plant lots of trees that are valuable for timber or fruit, rather than having the diverse suite of species that are typical of a tropical forest. So, the tree island planting strategy will be more suitable in cases where the goal is to restore forest.

Natural recruitment of trees seedling in the understory of a canopy of planted trees.

Our results and those of others show that the tree island planting approach holds promise as a cost-effective forest restoration strategy in cases where there are seed sources nearby to colonize and animals to disperse them, and where the spread of tree islands is not likely to be slowed by fire or invasive species. But we need more long-term studies to judge whether tree islands will be effective in other tropical forest ecosystems and to test other questions, like how the particular tree species used affect forest recovery, or what is the best distance to leave between tree islands.

More broadly, our study shows that tropical forests can recover some species quickly but it will take many decades, or longer, for forests to fully recover. So, preserving existing rain forests is critical to conserve biodiversity and the services that intact forests provide to people.

Yes, carefully-planned tree planting can help accelerate tropical forest recovery. But, in many cases we don’t need to plant trees everywhere. Rather we should use restoration strategies that encourage trees to plant themselves.

To learn more about our research, read our new article in the Journal of Applied Ecology, visit our websites (Holl Lab, Reid Lab), or watch a 7-min. video below.

Karen Holl describes the tree planting restoration approach and our long-term experiment in southern Costa Rica.
Los investigadores principales describen el método de applied nucleation y nuestro experimento a largo plazo en el sur de Costa Rica.

Global pledges to restore forests face challenges, and need increased support

Matthew Fagan is an assistant professor in Geography and Environmental Systems at University of Maryland Baltimore County. Here he describes the challenges confronting countries as they attempt large-scale forest restoration, and why many countries will need help to fulfill their goals. For more information, read his new, open-access paper in Conservation Letters.

Degraded and deforested landscapes are widespread, and tropical forests are being lost at a rate of 15.8 million hectares a year. But there is good news—temperate forest area is increasing, and more and more countries are voluntarily pledging to restore vast tracts of degraded land. Restoring forests benefits biodiversity and society, and can combat global warming as well, as growing trees lock away carbon dioxide.

International interest in restoring trees to landscapes emerged out of policy discussions last decade, and resulted in the 2011 Bonn Challenge and the creation of voluntary national restoration targets by many countries. The Bonn Challenge seeks to bring 150 million hectares into restoration by 2020, and 350 million hectarees by 2030 (that’s roughly 700 million American football fields, 350 million rugby fields, 500 million FIFA football fields, or an area a bit larger than India).

Current Bonn Challenge pledges total some 172 million hectares. That’s a massive international commitment, and when you add in internal commitments by countries, the potential restoration area swells to 318 million hectares.

All that area voluntarily committed to restoration got my co-authors and I excited, but also skeptical—were countries really going to follow through on their commitments?

Fagan_RainforestBlowdown

A rain forest blow-down in northeastern Costa Rica, with a storm-downed tree cut to clear a path. Silviculture restoration promotes the recovery of disturbed forests like this one. Photo credit: Matthew Fagan.

To try to answer that question at this early stage, myself, Leighton Reid (Virginia Tech), Maggie Holland (UMBC), Justin Drew (UMBC), and Rakan Zahawi (University of Hawaiʻi at Mānoa) asked three related questions in a recent paper in Conservation Letters.

  1. Is the amount of land a country pledged to restore related to their past record of restoring forested landscapes and implementing sustainable development?
  2. For the small group of countries that have publicly reported their progress on commitments, is the amount of restoration they completed predictable by their development level or other risk factors, like deforestation?
  3. Which countries will likely face the greatest challenges to meet their commitments and maintain restored land into the future?

We then set to gathering published information on country commitments and progress, and recent national rates of forest loss, agricultural expansion, and forest recovery.

Fagan_NaturalRegeneration

Recent natural regeneration in northeastern Costa Rica of varying ages. Photo credit: Matthew Fagan.

All of these programs seek to reforest landscapes in ways that benefit both nature and people, including options like natural regeneration (letting natural forests recover and expand), silviculture (interventions to restore standing forests, like preventing forest fires and promoting recovery from selective logging), tree plantations (often tree monocultures to produce timber and pulp on degraded lands), and agroforestry (planting trees on and around farmland to shade crops or protect streams and fields). These options are not all equal in their benefits for biodiversity, carbon, and society, but a diverse menu of options allows countries to consider committing to at least some form of restoration over large areas.

Fagan_VochysiaPlantation2

A tree plantation in northeastern Costa Rica funded by the national payments for environmental services program. It is a monoculture of a single native species, Vochysia guatemalensis, grown for timber. Photo credit: Matthew Fagan.

In a nutshell, what we found was both discouraging and encouraging.

First, after adjusting for the size of a country and how much restoration they had done previously, we found that less-developed countries committed more land for restoration. This might be for positive reasons; for example, they may be taking proactive action against the greater risk they face from climate change. Or it might be because they underestimated how challenging it would be to achieve a large pledge.

Fagan_Silvopasture

Silvopastoral restoration, a type of agroforestry, in northeastern Costa Rica. The understory is a cattle pasture, while the overstory is plantation of a native tree species, Dipteryx panamensis. Photo credit: Matthew Fagan.

Second, for twelve early-reporting countries, restoration progress was predictable based on a risk index. Countries with higher risk (risk factors included deforestation rates and progress on sustainable development goals, among others) had less restoration progress.

Third, countries made massive individual commitments that will be hard to achieve without wholesale transformation of their food systems. One third of countries committed >10% of their land area (with a maximum of 81%, in Rwanda). A quarter either committed more area than they had in agriculture, or committed more area than they had in forest. And one quarter of countries had more forest loss and agricultural conversion in 2000–2015 than their restoration commitment for 2015–2030.

Fagan_ShadeCoffee

Coffee plantation under tree cover, a type of agroforestry, in central Costa Rica. The understory is a monoculture of coffee shrubs, while the overstory is scattered planted trees. The partial cover helps the shade-loving coffee plants stay healthy, but many coffee farmers are moving away from this traditional farming approach. Photo credit: Matthew Fagan.

As noted in our paper, “If voluntary commitments like the Bonn Challenge fail to precipitate meaningful restoration across large areas, the UN’s vision of a sustainable future will become less attainable.” But what this study found is not countries that have failed on their restoration pledges. We are still in the first days of the UN Decade of Ecosystem Restoration. What we have identified is countries that will need help to restore their lands.

We believe it is time for the international community to step up and aid all countries in achieving their restoration goals. To quote Thoreau, “If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them.”

Fagan_Rainbow

A regrowing forest in central Costa Rica, showing the promise of restoration. Photo credit: Matthew Fagan.

Hard times for hemiepiphytes: Aroids have trouble making a comeback in second-growth forests

Estefania Fernandez Barrancos is a PhD student and Christensen Fellow at the University of Missouri St. Louis, where she is affiliated with the Harris World Ecology Center and the Center for Conservation and Sustainable Development at the Missouri Botanical Gardens. Estefania has previously written about how to restore bromeliad populations. Here she describes a recent study asking how well hemiepiphytic aroids recover in secondary forests in Panama.

Most people know aroids as the familiar swiss cheese plants found growing in hotels and shopping malls. But few people realize that the aroid family (Araceae) is the fifth most diverse plant family on Earth. These plants provide essential food and refuge for birds, bats, insects, and primates in tropical forests throughout the world.

Like many other plants, aroid populations are dropping because the rainforests where they live are being converted into farms. My new research shows that aroids are also slow to recolonize new forests that become available.

City Aroid Country Aroid

City aroid (left, Monstera deliciosa in a building), country aroid (right, Monstera sp. in a Colombian forest). Photo sources: Left Maja Dumat CCBY 2.0; Right – Thomas Croat via Tropicos.

Before I describe that research though, here is some botanical jargon for the uninitiated. Epiphytes (a.k.a. air plants) are plants that grow on other plants (but not as parasites). Hemiepiphytes are plants that grow on other plants but only for part of their lives. Many aroids are hemiepiphtyes because they start life in the soil of the forest understory and grow until they find a tree. Then they climb up the tree and live above the ground, but they always keep a connection to solid earth.

To study their recovery, I surveyed hemiepiphytic aroids in native tree plantations (9-years old), natural secondary forests (8-14-years old), and mature forests (>100-years old) near the Panama Canal. These forests are part of Agua Salud – a tropical forest restoration experiment led by the Smithsonian Tropical Research Institute. In the dense forest, I found aroids by looking for their stems coming down from the trees, then I followed the stem with binoculars until I found their leaves, which helped me identify the species. In all, I surveyed 1479 trees this way.

Estefania surveying mature forest tree Panama

Estefania Fernandez (below) and field assistant Carlos Diaz (above) look for aroids in a mature forest tree in Panama.

I found out that there were virtually no aroids in secondary forests or plantations. I recorded more than 2000 aroids from at least ten species growing on trees in mature forest, but in secondary forests and plantations I found less than 1% as many aroids and only three species.

Why do aroids have recovery troubles?

One reason for the lack of aroids could be that seeds from adult aroids in mature forests can’t reach the new forests. This seems unlikely because all of the secondary forests and plantations in my study were close to mature forests full of aroids, less than one kilometer away. Also, birds that are present in secondary forests are known to eat aroid fruits and disperse their seeds.

Another reason could be that the young forest canopy is too open for aroid seeds to germinate and grow. Unlike most plants, some aroids start out life growing away from light and towards darkness. (This has another great word: skototropism). It seems counterintuitive since most plants need light. But it is actually a good strategy. By growing away from light, aroid seedlings are more likely to run into a tree, which they need to climb up into the canopy and get to the light that they need to photosynthesize. So it is possible that there is too much light in the young forests and it keeps the aroid seedlings from finding a host tree.

Whether dispersal or establishment limits aroids in secondary forests, it is likely that more time will help. As forests become older and darker and birds bring in more seeds, aroid populations should eventually begin to recover. My research suggests that there is a considerable lag time required for aroids to recolonize disturbed habitats such as secondary forests and plantations.

More importantly, my study highlights how important it is to hold onto old forests. Forest restoration is a poor substitute for mature forest conservation. To the extent that we can prevent older forests from being cut down, it will help preserve many species of aroids as well as other plant and animal species that are threatened by habitat loss.

Aroid being pollinated by scarab beetles at Barro Colorado Island, Panama. Source: www.aroid.org.

You can read more about Estefania’s research in her new open-access paper in Tropical Conservation Science, or on other posts from Natural History of Ecological Restoration (here and here).

Things are not always better on the sunny side!

Chris Birkinshaw is an assistant curator in the Missouri Botanical Garden’s Madagascar Program, based in Antananarivo. He describes his observations on forest succession at Ankafobe, a site in the central highlands.

Anyone flying over Madagascar’s highly dissected central highlands will be struck at first by the vast grasslands that dominate this landscape.  But, those looking more carefully will also detect pockets of forest within the rich network of valleys.  These forests have a distinct fauna and flora but, perhaps because of their small size, they have attracted little interest from conservationists.  Consequently, in the last few decades, the majority have been degraded or entirely destroyed as their trees were cut for timber or charcoal and the relicts burnt by wild fires that rage over this landscape in the dry season.

The Ankafobe Forest, located some 135 km NW of Antananarivo, is currently being designated as new protected area by Missouri Botanical Garden’s Madagascar Research and Conservation Program.  It is one of the larger remaining areas of highland forest but, here too, the forest has been impacted by exploitation for timber and charcoal and burning by wild fires.

Efforts are underway to restore this forest to its former extent in the recent past.  This is no easy task because away from the current forest edge tree seedlings are subjected to harsh conditions: soils impoverished and compacted by annual burning, grasses that compete greedily for water and nutrients, an extended 7-month long dry season, and exposure to hot sunshine and strong desiccating winds.  Even when firebreaks are used to prevent wildfires from penetrating the grassland surrounding the forest, few tree seedlings naturally colonize outside of nurturing limits to the forest.

Few but not none.  A closer inspection of the landscape reveals some woody plants in the grassland on the less sunny south-facing slopes surrounding the forest (south is less sunny because Madagascar is in the southern hemisphere). Perhaps then the forest could be helped to expand by planting young trees preferentially on these slopes?

Ankafobe Forest South-facing on left.JPG

Vegetation is lusher on south-facing slopes (left) compared to north-facing slopes (right) at Ankafobe, a proposed conservation area in highland Madagascar.

To test this idea in 2017 we planted 25 nine-month old seedlings of each of four native tree species in grassland 20 m from the forest edge on both a south-facing slope and a north-facing slope.  The species were selected for this test are native to the Ankafobe Forest and were available at the local tree nursery when the experiment was installed.  After 12 months the survival and growth of these young plants were measured.

All four species survived well on the south-facing slope but only one species, Nuxia capitata, had good survival on the north-facing slope.  Mortality of Uapaca densifolia was total on the north-facing slopes.  Growth was sluggish on both the south-facing and north-facing slopes with the exception of Nuxia capitata on the south-facing slope that had a mean 12-month growth exceeding 20 cm.  These results suggest that south-facing slopes may provide the best results, at least at Ankafobe, for forest restoration endeavors.

South- facing North-facing
Species % Survival Average growth (cm) % Survival Average growth (cm)
Eugenia pluricymosa 72% 4.1 8% 3.0
Baronia taratana 88% 9.1 28% 12.4
Nuxia capitata 96% 21.5 100% 8.7
Uapaca densifolia 72% 10.5 0%

Aspect – the direction that a slope faces – makes a big difference for vegetation in the temperate zone, especially in dry places. But it is not often considered in tropical ecology. Directly or indirectly, the difference in sun exposure between the slopes at Ankafobe can make the difference between life and death for young trees growing in this hostile, water-stressed environment.

To read more blog posts about the restoration efforts at Ankafobe, please click here. You may also read a 2019 open access paper about seedling trials at this site here.

What can bat poop tell us about past tropical landscapes?

Rachel Reid is a postdoctoral researcher at Washington University in St. Louis. She uses isotope chemistry to answer questions about ecology, geology, and conservation – including questions that can help build reference models for ecological restoration. Note: This blog is republished with permission from Amigos (No. 91 May 2019), the newsletter of Las Cruces Biological Station.

 Many people head to Costa Rica for spring break to see monkeys and sloths at Manuel Antonio National Park or to try their hand at surfing in the Pacific. While we did stop to gawk at the crocodiles that hang out under the bridge over the Tárcoles River with a busload of tourists, the goal of our trip diverged significantly from the spring break crowd – we were heading off the beaten path to southern Costa Rica to collect samples of modern and ancient bat guano (aka poop).

Bats sometimes visit the same caves over thousands of years, and the accumulated piles of guano offer a unique opportunity to study past environments. Just like a core of sediment from the bottom of a lake or the ocean, a core of bat guano collected from a cave contains useful information about the past, both recent and distant. The material at the bottom of the core is the oldest and that at the top is the youngest, so by sampling the length of a core, we can essentially take a short, stinky walk back in time.

We are interested in detecting changes in bat guano chemistry (particularly the carbon isotope values) through time as a way of evaluating what type of vegetation would have been on the landscape in the past. This works because information about the plants at the base of the food chain gets propagated up to the plant-eating insects and then to the insect-eating bats whose guano we’re sampling.

Bat Food Chain

Like other animals, bats and insects both gain carbon and nitrogen through the food they eat. Bats eat insects, which are in turn eating the local vegetation. Different types of plants have different carbon isotope values, such that most trees and shrubs (C3 plants) have much lower carbon isotope values than most grasses (C4 plants). Shifts in tropical bat guano carbon isotope values, therefore, are indicative of landscape-level changes in vegetation between more open, grassland plants and tropical forest.

How does bat poop inform conservation?

In the late 1940s, southern Costa Rica was nearly 100% forested. We know this from aerial photos – the earliest ones are from 1948. In later years, aerial photos show that most of that forest was cleared for coffee plantations; two thirds of it was cleared by 1980, for example.

This recent deforestation has motivated forest restoration efforts such as the creation of biological corridors and international scientific studies. Nonetheless, several studies (such as this and this) suggest that extinction rates in this region may be lower than would be predicted from recent habitat loss. One explanation for this could be that the regional flora and fauna evolved for several thousand years in a mixed forest and non-forest landscape managed by humans. By piecing together records of past vegetation from bat guano cores, we’ll be able to gain a better picture of what the landscape would have looked like in the past and potentially refine landscape-scale conservation and restoration targets.

For this first trip, our goals were to visit several caves to collect samples and to scout out future sampling opportunities. Southwestern Costa Rica has the highest concentration of karst caves in the country, so we were in the right place. In four days of fieldwork we visited three different caves (two of them twice!), collected 77 cm of core material, and took dozens of samples of modern bat poop.

At Bajo los Indios Cave, also known as Corredores, along the Rio Corredor, we ventured into a restricted, elevated chamber in hopes of finding deeper, more protected accumulations of guano. We were disappointed to find that even in this higher chamber, the cave was very wet and muddy and any significant guano accumulations appeared to have washed away. We collected a guano/mud core anyway and we’ll see what we can learn from it.

Bat Guano Team by JF

The bat guano team. From left to right: Leighton Reid & Christy Edwards (Missouri Botanical Garden), Rachel Reid & Alice Xu (Washington University in St. Louis), and Jeisson Figueroa (Organization for Tropical Studies). Photo by Jeisson Figueroa.

Taking a guano core by JF

Leighton Reid uses a peat corer to extract a sample of bat guano from a karst cave. Photo by Jeisson Figueroa.

One additional important piece to our project is to try to get a better idea of what modern insectivorous bats, such as the mesoamerican mustached bat (Pteronotus parnellii mesoamericanas), are eating. We’ll then use that information to better interpret our results back in time. We’re excited to start analyzing samples!

This pilot study was generously funded by grants from the Living Earth Collaborative and from the International Center for Energy, Environment and Sustainability.

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!

 

 

It’s Complicated: Trees and Ecological Restoration

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The best time to plant a tree was twenty years ago. The second best time is now.
-Anonymous

Addendum: That is, unless the tree will grow just fine without your help or the tree doesn’t really belong there. In that case, the best time might be never.

Planting a tree is rejuvenating. It gets you outside, it’s good exercise, and it’s often good for the planet. Really, trees give us an awful lot and don’t ask for much in return. Among their many gifts are food, shade, animal habitat, building materials, erosion control, and fuel. Trees also filter our water and suck carbon out of the air. In cities, trees collect grit and grime that would otherwise coat our lungs.

But tree planting is not the same as restoration. Ecological restoration is the process of assisting the recovery of a damaged ecosystem. Trees are integral to many ecosystems, like forests…

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