Shaw Nature Reserve’s Dark Diversity

There are almost 3000 species of vascular plants in Missouri. Which ones should we conserve at Shaw Nature Reserve?

One of the most challenging questions in restoration ecology is what species should live in a restored habitat? When we assist ecosystem recovery by removing invasive species or applying prescribed fire, for example, some plant species reappear on their own. They emerge from seeds that were dormant in the soil, or they are transported in from elsewhere by wind, water, or animals. But other species require assistance.

In ecology, the set of species that could live in a given habitat but are currently absent is called “dark diversity”. Quantifying dark diversity can help set restoration targets by highlighting gaps in species composition. A starting point for calculating a site’s dark diversity is to take a regional species list and subtract out the species present at the restoration site.

To take an example from near the top of the alphabet, at Shaw Nature Reserve, we have observed one species of false foxglove (Agalinis tenuifolia; the most common species statewide) out of nine that are known to occur in Missouri. Of the other eight, seven are known from the same county as Shaw Nature Reserve or from adjacent counties, and all occur in habitats like glades, woodland edges, and prairie swales, which we have restored or reconstructed. It may be reasonable to include these seven species in our enumeration of Shaw’s dark diversity and consider them as candidates for (re)introduction.

Why haven’t these seven missing Agalinis species appeared spontaneously? If they were once present at Shaw, were their seed banks depleted by decades of cattle grazing prior to Missouri Botanical Garden’s purchasing the property in 1925? Are they now unable to disperse to Shaw on their own? This seems likely as Shaw is situated in a fragmented landscape, and Agalinis species do not have any obvious mechanisms for long-distance seed dispersal. Another possibly, not mutually exclusive, is that local environmental conditions are unsuitable. Important symbionts in the soil might be absent, or appropriate host plants, since Agalinis species are hemiparasites that latch onto other plants’ roots to steal sugars.

Climate change makes it even more difficult to think about how to restore a site’s dark diversity. For instance, green false foxglove (A. viridis) is currently found far to the south of Shaw Nature Reserve, in southern Missouri, Arkansas, Louisiana, and Texas. But even optimistic climate models suggest that by 2070 Franklin County, MO may feel more like present-day Franklin County, AR – a county where A. viridis has been collected.

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Aotearoa: Predator-free by 2050?

James and Thibaud Aronson post here their second report on ecological restoration in New Zealand, an island nation that seeks to eradicate non-native predators by 2050.

The government of New Zealand (or Aotearoa, as the Maori call it) has announced its goal to be predator-free by 2050, but the effort and expense required to eradicate the tens of millions of noxious animal and plant pests from the entire country is mind-boggling.  One important development is technological in nature. Invasive mammal-killing traps are not very costly, but they do require regular maintenance. Some companies, such as this one, are designing and manufacturing automatic traps that humanely kill pest animals and then reset themselves.

There are still many obstacles to achieving a predator-free New Zealand, but the situation would be far worse today if not for impressive political will and public buy-in.

Much of the native fauna has only survived to this day because, in addition to the two main islands, New Zealand also possesses many small offshore islands, some of which were never reached by introduced pests, like rats and stouts. Eradication campaigns have for many years been carried out on various islands relatively near to shore, to make them ‘pest-free sanctuaries’, where small salvage populations of rare and endangered species have been translocated and established successfully. Several ‘mainland islands’ have also been established, on North Island and South Island, completely surrounded by massive pest-proof fences, with ongoing trapping and poisoning efforts to eliminate any predator that might manage to get in.

We visited Tawharanui, one such sanctuary in the north of the country. While it is in an area that still has some native forest, the contrast is remarkable as soon as one passes the fence. The first notable difference is an audible one. The birds of New Zealand are unusual in that they sing all day long, and they are loud. James Cook, the first European to set foot on the islands, described the birdsong as “deafening”. Today, most of the forests are quiet, and the few birds that can be heard are exotic species, introduced by nostalgic, home-sick Europeans. Tawharanui gives an idea of what things once were like. Within minutes, we were struck by the diversity and abundance of life, another world entirely compared with the unprotected and second growth forests. Half a dozen endemic species thrive here that can hardly be encountered anywhere else on the mainland, and all of them display the characteristic fearlessness that has caused their downfall.

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A North Island robin (Petroica longipes), displaying the typical inquisitive behavior that has caused the extinction of so many insular birds worldwide.

A few days later, we took a boat to Tiritiri Matangi (“a place tossed by the wind” in Maori). This small island, an hour away from Auckland, is one of the country’s most famous wildlife sanctuaries, and a remarkable experiment in ecological restoration. It was intensively cultivated and pastured until 1971, when it passed back to government ownership, with the intention of making it a nature reserve. However, as natural regrowth was very slow, a massive volunteer program was launched in 1984, leading to the planting out of over 250,000 native trees in the next ten years. Under the guidance of Dr. John Craig, and colleagues, 25 years of work at Tiritiri Matangi has led to much restoration of both natural and social capital.

A key component was a large-scale pest eradication program applied with great thoroughness. Once the habitat was deemed suitable, several endangered species were translocated from other more isolated islands where they persisted, nearly all of which have since established successfully. The regenerating forest offers great opportunities to view the wildlife, and tens of thousands of people visit the island every year. The success of the project has since led to similar projects on other offshore islands in New Zealand.

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The stitchbird (Notiomystis cincta), the sole representative of its family, was once common throughout New Zealand. Within a century of the Europeans’ arrival, only a few hundred birds persisted on a single offshore island. It has since been translocated to Tiritiri Matangi and several other pest-free islands.

New Zealand’s best tool in this struggle is probably its people. Great efforts have been made in communicating to children the uniqueness of their endangered species, and how essential is the eradication of the introduced pests, no matter how cute and cuddly they may be. This was true at Tiritiri Matangi, and everywhere else. See the two key references cited at the end.

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A sign describing one of many community programs we saw, where locals carry out conservation work, such as this eradication program along the Kepler Track, near Te Anau, South Island.

Invasive exotic plants are also a serious obstacle to ecosystem recovery, especially various species of introduced conifers that have escaped commercial tree crop plantations and become naturalized and out-of-control on native grasslands little prepared for such an encroachment. But the use of native plants has really taken off, with sophisticated, and inspiring native plant nurseries found throughout the country, and everywhere from city gardens to public works projects, native plants being used more and more every year. As a result, native species, from green geckos to tuis, the country’s most famous songster, can now be seen right in the middle of Auckland.

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A Tui (Prosthemadera novaeseelandiae) perched on a native Hebe shrub on Stewart Island.

Stewart Island, the country’s third largest island at 1750 km2, is an example of what the country as a whole could aspire to. Royal albatrosses come into the harbor following fishing boats, blue sun orchids bloom on the roadsides, and kiwis come out at night to forage on the rugby field.

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Oban, the only settlement on Stewart island. Walk in any direction out of town, and you quickly find yourself entering the surrounding national park.

 

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A blue sun orchid (Thelymitra venosa), blooming on a roadside embankment on Stewart Island.

 

Now, of course, only 400 people live permanently on the island, 85% of which is a National Park, and most people on the island depend on tourism for income. The model obviously cannot be translated directly to the country as a whole. All dogs on the island must receive kiwi-avoidance training, and when a pair of variable oystercatchers decided to nest on the field in the middle of the primary school’s playground, the area was cordoned off, and several signs put up, telling children what a privilege it was that their school had been chosen by the parental pair, and to keep well away from the nest. The chick hatched while we were there, and happily crossed over the road safely, with his parents following the reckless chick, to the nearby beach. There too, even though people (but not dogs) are present every day and evening, except when it’s pouring down rain, these birds are nearly guaranteed a watchful and caring stewardship on the part of the locals and quickly tuned-in visitors. These simple things show a will on the part of the local people to exist within the native ecosystem, rather than imagining themselves outside it, and licensed to do whatever they will, and to hell with the consequences. The rest of the world would do well to take a page from NZ’s book.

 

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Newborn variable oystercatcher (Haematopus unicolor) on the beach, 50 meters from Oban’s main hotel.

Additional recommended reading

Craig  J,  Mitchell  N,  Walter  W,  Galbraith  M,  & Chalmers  G. 1995. Involving people in the restoration of a degraded island: Tiritiri Matangi Island. In: Saunders DA, Craig JL, & Mattiske EM, editors. Nature Conservation 4: The role of networks. Chipping Norton, NSW, Australia, Surrey Beatty & Sons. Pp. 534–41.

Craig J, & Vesely E 2007. Restoring natural capital reconnects people to their natural heritage: Tiritiri Matangi Island, New Zealand.  In: Aronson J, Milton SJ, & Blignaut JN, editors. Restoring natural capital: science, business, and practice. Washington DC, USA, Island Press. Pp. 103–111.

What’s going on in the Land of the Long White Cloud?

James and Thibaud Aronson post here the first of two reports from New Zealand, where they spent the first three weeks of January 2017, learning about the remarkable restoration and conservation work going on there.

New Zealand, or Aotearoa (Land of the Long White Cloud, as the Maori call it), is one of the world’s leaders in terms of conservation and restoration. However, it certainly did not start off that way.

New Zealand was first settled by Polynesian sailors about 750 years ago, one of the last places on Earth to be colonized by humans. These pristine islands, which had stood in isolation for 80 million years, harbored a wealth of unique lifeforms, from the iconic kiwi (of which few people know there are in fact 5 species), to the weta (cricket relatives in one of several genera endemic to New Zealand, some of which  are among the largest insects in the world), and the tuatara, large, endemic, lizard-like reptiles, the last survivors of an order that thrived 200 million years ago.

The island did not lack predators: just think of the now-extinct Haast’s eagle (Harpagornis moorei), the largest eagle to have ever lived, and the fierce, flightless moa (nine species in six genera; all extinct), giant relatives of the ostrich, the biggest of which stood fully 3.6 meters (12 feet) tall and weighed 230 kg (510 lb). However, Aotearoa harbored practically no land mammals, the only exceptions being two species of bats. Therefore, many native animals were flightless, absolutely unafraid of humans and their dogs, and thus very easy to hunt.

Faced with this incredible boon, the Maori did what humans have done on every single island and continent they have ever reached: they took and took without restraint. All 9 species of moa, the most rewarding of prey, were gone within 200 years. Seals, once abundant along all coastlines, vanished from many areas. Forced to change their ways, the Maori shifted to eating more fish and shellfish, and took to cultivation, burning down forests for cultivation, and also started eating the bracken fern that grew back in abundance after fires. However, and very unusually, having caused widespread extinctions, the Maori eventually introduced rāhui, a strict system of preventing all unauthorized persons  to enter an area, or harvest a specific resource. The intention was to allow regeneration, such as certain animal food sources, or plant materials – such as wood from a certain tree species prized for carving,  thus avoiding local depletion of resources or even further extinctions. This system is still in use today among Maori, and can also be declared by different agencies of the NZ government!

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Billy Boy, a Maori guide in the Waipoua forest, whose connections to New Zealand’s wilderness is an essential part of his identity. Whenever one of his grandchildren was born, the first thing he did was to take them to the forest and begin their introduction to the natural world.

However, things took a significant turn for the worse 200 years ago, when Europeans reached New Zealand. They rapidly established large-scale logging activities, targeting the various species of native conifers, which can live for millennia and reach enormous sizes. For a few decades, whaling and sealing were vastly profitable as well, until populations crashed. What’s more, the Europeans brought with them cats, black rats, and later possums, stoats, and other carnivorous mammals. All of these species have since gone feral, and become one of the foremost ecological problems the country faces today. Since human settlement, 47 endemic bird species have gone extinct, about half from Maori over-hunting, and the remainder in the last 2 centuries, wiped out by feral predators, as were various species of reptiles, amphibians, and invertebrates. Many more species have no doubt suffered the same fate, disappearing before they were even documented.

However, in recent decades, New Zealand has made an impressive and inspiring commitment to preventing future degradation and in fact taken many great strides towards rolling-out restoration at a national scale. This merits celebration and emulation. During our 3-week trip, we got to see first-hand some examples of the conservation and restoration work underway.

One of the most iconic trees of New Zealand is the kauri (Agathis australis). These massive conifers once dominated the forests in much of the warmer, nearly subtropical, northern part of the country. They can live well past a thousand years, grow 50 meters tall, and reach a girth comparable to that of the Californian sequoias. The largest individual known today is called Tane Mahuta, or Lord of the Forest, the name of one of the main gods in Maori cosmology. It is hard to describe how insignificant one feels when standing below these giants.

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Te Matua Nhgahere (Father of the Forest), the oldest and second-largest remaining kauri in New Zealand. The age of this tree is variously estimated to be between 1200 and more than 3000 years old. Such longevity is exceedingly rare in tropical or subtropical rainforest trees.

The kauri also happen to yield excellent timber, once particularly valued for ship-building. Their logging was only banned in 1972, and less than 4% of the original kauri forests are left today. Happily, no native forest can be legally logged anywhere in New Zealand today, thanks to an election promise of the Labour government which passed into law in 2002.

Waipoua forest, on the north-west coast of the North Island, is the largest kauri forest left in New Zealand. Great efforts are being made today to preserve the remaining stands, particularly focusing on halting the spread of kauri dieback disease, a horrific, recently-arrived fungus-born infection that spreads through soils and kills every kauri tree it infects. Part of the campaign to save the tree entails education and consciousness-raising among all visitors to the kauri forests as to the importance of cleaning their shoes and boots both when entering and leaving the area.

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Skeleton of a kauri killed by the dieback disease in Waipoua forest. Can the disease be stopped?

Some forest areas have fared better, such as the Nothofagus forests of Fiordland National Park, in the south-west of the South Island, well protected as they are by billions of biting flies, which have successfully prevented any significant human settlement in the area. However, stoats, rats and possums are not so easily deterred, and the whole area is a prime example of empty forest syndrome.

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Southern Beech forest (Nothofagus spp.) in Mt Aspiring National Park.

Therefore, enormous amounts of money are being spent on large-scale trapping and poisoning throughout the country, to try and control these non-native pests which wreak havoc both on native fauna and flora. For instance, we visited the private Pupu Rangi Sanctuary, 100 hectares of forest south of Waipoua, in the North Island. Its owner, Octavian Grigoriu, and a diverse team of volunteers work tirelessly in the forests, maintaining traps and poisoned bait around the whole perimeter of the forest, and deep in the bush as well. Octavian hosts paying guests, which helps pay for the expensive traps and poison. As a result, native species, including the North Island brown kiwi, are doing significantly better than in the nearby Waipoua forest, which is much larger, and therefore exponentially harder to protect effectively.

In sum, all over New Zealand, many initiatives, both top-down and bottom-up, are doing excellent work, which we will discuss in our second blog post.

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Octavian Grigoriu setting possum bait laced with cyanide in his privately-owned forest reserve.

 

Little known side of Hong Kong: Conservation and Restoration work at Kadoorie Farm and Botanic Garden (KFBG)

James and Thibaud Aronson made a stop in Hong Kong recently, and post a report on what’s going on restoration-wise at the 60-year old Kadoorie Farm and Botanic Gardens.

After three weeks in New Zealand – about which we will report in our next two posts – we stopped recently in Hong Kong to visit the Kadoorie Farm and Botanic Garden (KFBG), which has just celebrated its 60th anniversary. Most visitors to Hong Kong never leave the city center, which has the second highest concentration of skyscrapers in the world and rivals London and New York for shopping, but also as a global hub for finance, trading, and marketing. But, we were lucky: through our friend Kingsley Dixon we had an introduction to Dr. Gunter Fischer, Head of the Flora Conservation Department at KFBG. Dr. Fischer came to Hong Kong from Austria, 7 years ago, and now oversees the vast – and gorgeous – botanic garden, the herbarium, the genetic and ecology laboratories and the various restoration and native plant recovery programs at the KFBG, which is the result of an exemplary public sector-private sector partnership. Behind the scenes, a key component is the large on-site tree nursery and enormous amounts of effort devoted to seed collecting and plantations of mother plant collections of rare native tree species for seed production. “In a changing world, resilience comes from diversity”, as Gunter so nicely puts it.

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Ms. Chung Yick Kwan, an employee of the garden working in the KFBG tree nursery, handling one of the many rare native species propagated here.

Other departments at KFBG include the Sustainable Living and Agriculture, Fauna Conservation, Kadoorie Conservation China, and Education. Activities are devoted to developing and demonstrating sustainable small-scale farming methods for food production in South China, including new methods such as permaculture and traditional Chinese methods that have been lost or abandoned during the Chinese cultural revolution. There is also an extensive rehabilitation program for wild animals, notably many rare and endangered turtles, mammals, and birds that were seized by Hong Kong customs or delivered by animal rescue organizations.

All of these activities stem naturally from the original raison d’être of the organization. When Sir Horace and his brother Lord Lawrence Kadoorie founded the Farm 60 years ago, their goal was to help Chinese immigrants get established as small farmers.

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Sir Horace and Lord Lawrence Kadoorie – the founders of KFBG. (Photo: KFBG archives)

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Text of one of the guiding principles of the charity work of KFBG in the early 1950s, which is still valid in the 21st century (NB. In the 1950s KFBG was called KAAA, Kadoorie Agricultural Aid Association). (Photo: KFBG archives)

To this day, the Kadoorie Foundation is the main funding source of the KFBG. But with vastly greater affluence in Hong Kong today, since the mid-1990s, a decision was made to transform the property into a world-class education and conservation center with a botanic garden at its heart. The conservation work comprises numerous projects in Hong Kong and mainland China but also parts of Southeast Asia, such as poorly explored regions of Laos and Cambodia.

Originally, Hong Kong was covered in tropical and subtropical forest, but it was completely deforested after the British took over in 1841; visitors in the 19th and early 20th century called Hong Kong a “barren rock”. As a result of centuries of cultivation with crops such as rice and tea, and ongoing urbanization in combination with more and more exhausted soils, many mountain slopes were left to their fate, completely denuded of any vegetation ongoing soil erosion, and high run-off during the annual monsoon seasons caused landslides and wreaked havoc.

Starting in the 1880s, successive governments undertook massive afforestation programs, as documented by the eminent ecologist Richard Corlett. However, during the World War II Japanese occupation of Hong Kong, most of the recently recovered forests were burned or devastated by harvesting of fuel wood.

After WWII, secondary forests began to recover, but of the 450 native tree species, only ca. 100 regenerated naturally, and the other species carry on sadly towards extinction. Moreover, there are huge problems with introduced grasses, many of which carry fire far better than anyone would like.

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Upper area of KFBG’s restoration site devastated by a fire in 2004. (Photo: Dr. Billy Hau)

Thus the challenges for conservation and restoration are enormous. Indeed, the same is true at the regional scale. As Gunter told us, “most of the forests of South China have been trashed”; only tiny fragments of primary forest remain, and very little work on restoration of the original forest is going on. Since he arrived at KFBG, over 6 years ago, Gunter has done remarkable things in the botanic garden portion of the 159 hectare property, located on a steep slope of Tai Mo Shan, the highest point in Hong Kong (957 m or 3140 ft), including the launch of an ambitious restoration program on the recovering wilderness portion of the property that few visitors see. Rather than full coverage, a tree island, or assisted nucleation approach is taken, similar to that used in on-going experiments in Costa Rica, which Leighton Reid posted on last November.

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Core area of the 15 hectare (42 acre) experiment restoration site at KFBG, showing tree island plantings of 2015 and 2016, with various soil preparation techniques and tree guards being tested. (Photo : Gunter Fischer)

The focus is largely scientific and conservation-oriented, given that most of the flora of Hong Kong is highly endangered. However, horticulture and arboriculture are as important as ecology here, Gunter assures us – an observation that jives well with the Missouri Botanical Garden’s approach to restoration as well. For example, Gunter and his colleagues not only plant ten thousand trees on average each year, all produced in the experimental KFBG nursery, they also prune and shape the trees they’ve planted to encourage upward growth rather than low shrubby formatting, which is what often happens with many trees after planting.

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Structurally pruned Quercus edithiae, a rare canopy tree in South China.

A large proportion of the tree planting budget is devoted to plastic cylinders (tree guards/shelters) to protect tree saplings from barking deer and wild boar, but also from harsh climatic conditions.

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Tree guards used to protect seedlings on a ridge from strong desiccating winds.

The KFBG restoration team also makes a big effort to study soil improvement techniques that will compensate for degraded soils and improve survival and early growth of the planted trees. One of the most interesting components of this experimental work concerns the use of Biochar prepared on site, by slowly heating wood in closed containers with almost no air. Much of the wood comes from stems and trunks of intentionally introduced and now invasive fast-growing trees, such as the appropriately named Acacia confusa, that are gradually being removed from the property. This approach to invasive woody weeds has great potential in many parts of the world and should receive a lot more attention and investment.

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Invasive trees and those deemed hazardous to human safety are continuously removed and replaced with native species. The wood is used to prepare biochar.

Clearly, KFBG is one of the bright spots of plant and animal conservation, and ecological restoration in Asia today.

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Native animals such as this bamboo pit viper (Trimeresurus stejnegeri) are recolonising the restoration site. (Photo: Gunter Fischer)

For more information, see the recent article published by Gunter and his colleague Jinlong Zhang. Also, if you’re travelling to Hong Kong, be sure to stop by. Even if you don’t trek to the higher slopes to see restoration work-in-progress, the Botanic Garden is also full of interesting natural and cultural sights and stories too, such as these elevated pigeon hotels. And how many botanical gardens occasionally have to close a road because a massive python is stretched right across it, digesting a deer for a week!

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Dragon boat pigeon hotel on the KFBG grounds.

And there is the museum, theme gardens such as the Gloria Barretto orchid sanctuary, and lush forest gardens that appear to be native forest fragments but in fact are tropical gardens providing an exhilarating experience for thousands of visitors each month just a few miles from downtown Hong Kong.

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Montane streamside forest garden with trees covered in epiphytic ferns.

 

 

Vascular epiphyte restoration using bromeliad transplants in Southern Costa Rica

Estefania Fernandez is a Bascom Fellow who recently finished her master’s thesis at the University of Montpelier, France. Last year, Estefania wrote about her preliminary results on tropical forest restoration and vascular epiphyte reintroductions in Costa Rica. Here, she describes the final results, recently published in Restoration Ecology.

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A transplanted bromeliad, Aechmea dactylina flowering in a 10-year old tree plantation.

Vascular epiphytes are plants that germinate and root on other plants without taking their nourishment from their host plant, and they represent 50% of the flora in some tropical forests and 9% of all vascular plants worldwide. If you are a plant lover, then you most likely have one or several vascular epiphytes in your house. Some of the most appreciated horticultural families include orchids (Orchidaceae), aroids (Araceae), and bromeliads (Bromeliaceae).

Vascular epiphytes also play key roles in our ecosystems. They are crucial to forest water and mineral recycling as they intercept rainfall and prevent rapid run-off and nutrient leaching. Vascular epiphytes are also exceptional microhabitats where invertebrate communities find refugia and birds and arboreal mammals forage.

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Transplanted individual of Werauhia gladioliflora

Despite their importance in forest ecosystems, vascular epiphytes are rarely taken into account in forest restoration. This is problematic because vascular epiphytes are often among the slowest plants to recolonize regenerating forests.

In 2015-2016, I tested whether transplanting epiphytes into young restoration sites could be a viable strategy to accelerate their reestablishment. I used a bromeliad for my experiment, Werauhia gladioliflora (H. Wendl.) J.R. Grant, which was common in remnant forest but had not been found during epiphyte surveys in nearby restoration areas. In March-June 2015, I transplanted 60 bromeliads into three restoration plantations near Las Cruces Biological Station in southern Costa Rica. I revisited the sites in January-February 2016, nine months after transplantation, to monitor survival and arthropod recolonization.

Happily, over 75% bromeliads survived and the number of arthropods on branches with bromeliads was seven times greater than in branches without bromeliads. Additionally, I observed that bromeliads buffered the local microclimate; during the driest and hottest times of the day, the interior of the bromeliads was moister and cooler than ambient air.

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Transplanted individuals of Werauhia gladioliflora (left) hosted considerably more arthropods in their rosettes than could be found on the stems of trees that had not received a transplant. GN, JG, and MM are three study sites near Las Cruces Biological Station in southern Costa Rica. Photo by Dave Janas.

Restoring arboreal refugia

My research suggests that transplanting fallen epiphytes onto trees in restored sites contributes to the recovery of vascular epiphyte diversity in these ecosystems and has the additional benefits of bringing back arthropod diversity to these sites. Epiphytes, and specifically “tank” epiphytes that retain water in their rosettes, help stabilize microclimatic conditions, a critical function in light of climate change, which may put arboreal communities at special risk. Indeed, the body temperature of many animals such as invertebrates entirely depends on ambient temperatures but rising temperatures could push arboreal animal communities to the ground. Epiphytes offer ideal refugia from high temperatures and drought and their presence in tree canopies and understory is critical to preserve arboreal animal communities. Transplanting other epiphyte families or even entire epiphyte communities found on fallen branches could be tested in the future to broaden this strategy.

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Estefania inspects a flowering individual of an Aechmea dactylina transplant

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

Cactus conservation and restoration of arid environments in Central Mexico

En route to attending the 4th meeting of the Ecological Restoration Alliance of Botanic Gardens Conservation International, in Xalapa, Veracruz, Mexico, James Aronson stopped off to visit Beatriz Maruri Aguilar, a recent Bascom Fellowship recipient who works as Scientific Research Coordinator at the Cadereyta Regional Botanic Garden, and her colleagues, Director Emiliano Sanchez Martinez, and Research assistants Hailen Ugalde de la Cruz and Hugo Altamirano Vázquez in Cadereyta de Montes, Queretaro, north of Mexico City. Beatriz and Hailen describe the Garden’s work conserving an endangered, endemic cactus, and an innovative restoration project.

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Main entrance to Cadereyta Regional Botanic Garden

Cadereyta de Montes is close to the southern end of the Chihuahuan Desert, in the semiarid zone of Queretaro and Hidalgo. The place is relevant for biodiversity because of its number of endemic arid plants. However, today some habitats have been definitively altered and several special plants are on the brink of extinction.

One of those emblematic species, popular among succulent plant collectors around the world, is under severe threat to its survival. Worldwide growing successfully in cultivation, Mammillaria herrerae Werderm. is facing tough conditions and could eventually disappear from its original habitat. Scientists from the Cadereyta Regional Botanic Garden have done a survey which indicates that there are only a few hundred individuals remaining in the wild, that the species shows very low recruitment by seed, and that seedlings grow on rocky substrates beneath nurse plants.

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Expedition day: James and Beatriz descend the slopes where Mammillaria herrerae lives. Photo by Hailen Ugalde de la Cruz.

Observing the remaining individuals is a shocking experience that moves to reflection.

They look small and fragile, but these geometric, almost spherical, plants are a beautiful example of the precision of nature, which gives each organism the characteristics it requires to survive in its natural habitat.

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The beautiful Mammillaria herrerae Werderm., also known as “golf ball cactus” or “bolita de hilo” (small ball of thread). Photo by Beatriz Maruri Aguilar.

Densely covered with white spines and half-buried in the rock, Mammillaria herrerae hides its presence in the limestone soil. Its densely-distributed spines also help harvest fog at this elevation, where atmospheric moisture can condense. In an arid region like central Mexico, such adaptations provide species with strategies to reach the vital element.

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A small group of Mammillaria herrerae struggle to persist on the steep slope. Photo by Hailen Ugalde de la Cruz.

Their permanence wouldn’t be menaced, but infrastructure development has reached them.

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The pipes of the “Acueducto II” Hydraulic system climb more than 1200 meters to reach an elevated point from which it carries water by gravity to Queretaro City. Photo by Beatriz Maruri Aguilar.

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In such a challenging environment, the construction of this infrastructure has severely damaged the landscape where Mammillaria herrerae lives. Photo by Beatriz Maruri Aguilar.

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As the aqueduct was constructed over several years, several efforts were conducted to relocate bigger native plants. Photo by Hailen Ugalde de la Cruz.

Efforts will continue. The Cadereyta Regional Botanic Garden team will conduct a 2-year demographic study, study the floral biology of the species, and describe plant community biodiversity at the specific distribution points. Stock propagation at the Garden will continue. The path is being prepared to, one day, return these jewels to their place in their natural environment, and to protect them better in situ.

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Hailen Ugalde (left), Hugo Altamirano (center), and Beatriz Maruri (right), the staff of the Cadereyta Regional Botanic Garden, visit a remnant population of Mammillaria herrerae . Photos by James Aronson (left) and Hailen Ugalde de la Cruz (right).

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The landscape around M. herrerae’s natural habitat. The mountain in the background is the southern facies of the Sierra del Doctor, part of the Sierra Madre Oriental. Photo by Hailen Ugalde de la Cruz.

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Some of the globose companions of Mammillaria herrerae Werderm. Left: Astrophytum ornatum (DC.) Britton & Rose; Right: Mammillaria parkinsonii Ehreb. Photos by Hailen Ugalde de la Cruz.

“An unusual model of assisted ecological restoration”

At first sight, the arid scenery of the surroundings of the small city of Cadereyta, in Queretaro, Central Mexico, could transport us to past times.

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Panoramic view from Cadereyta de Montes, and the ancient flavor of the streets. Photos by José Belem Hernández Díaz.

However, this semi-urban and semi-rural zone combines the features of ancient Mexican villages and landscapes with the unmistakable signs of the transformation that progress usually brings.

The peripheral landscape of Cadereyta de Montes (14,000 inhabitants) is showing signs of transformation. The urban area is gradually displacing the agricultural parcels and the native flora, giving rise to an interface formed of irregular patches that combine new houses and small agricultural parcels. A third type of ground, neither agricultural nor urban, is also present. This type of land is isolated from wild and agricultural areas, and can degrade easily.

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The polygon of the Cadereyta Regional Botanic Garden, highlighted in yellow, in the vicinity of Cadereyta de Montes. Map prepared by Beatriz Maruri Aguilar.

In additional to its formal collections and buildings, the Cadereyta Regional Botanical Garden maintains an area that exemplifies the conditions found in much of the surrounding semi-arid region. Xerophytic shrub-dominated matorral is the main vegetation type which is generally highly degraded by human activities over the last decades, and surviving remnants in good ecological condition are only found quite isolated from agricultural areas. The vegetation comprises an interesting assemblage of native species in the Asteraceae, Poaceae, Solanaceae, Verbenaceae, Euphorbiaceae, Cactaceae, Fabaceae and other families, many of which are struggling to survive within large patches of invasive grasses.

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A view from the top: looking down at degraded land to be managed by the Botanic Garden. Photo by Hailen Ugalde de la Cruz.

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Another view from the top: Hugo, Beatriz, and James observe the transformed landscape of Cadereyta de Montes from one of the Garden’s balconies. Photo by Hailen Ugalde de la Cruz.

In this area, the Botanic Garden is working on restoration models that will be of interest – and direct use – to local landowners. It is an unusual model of assisted ecological restoration, with an agroforestry approach. The core idea is that through the implementation and monitoring of native vegetation and economic plant mosaics, it should be possible to combine conservation of biodiversity, sustainable development for small farms, and ecological restoration of degraded lands.

The pilot project will have two different types of parcels for comparative and demonstration purposes. One type will be built following an ecological approach to restoration, using only native plant species; the other will have an agroforestry approach, combining a group of native species with some selected edible/useful species. The area of the plots where the two strategies will be implemented will be prepared by removing an invasive species of grass (Melinis repens Willd. (Zizka), or “pink grass”). The agroforestry model will also generate useful products, such as agave leaves, which are used in the region for several purposes including to make pulque – an ancient beverage made by the fermentation of the agave sap, highly popular in this region. This model will also include aromatic plants – such as the asters Matricaria chamomilla L. and Calendula officinalis L. and the mint Salvia sp., as well as other useful plants as the euphorb Jatropha dioica Sessé, “sangregado”, commonly used as an ingredient in shampoos and formulas against gray hair.  These human uses are valuable in areas like this, where some human populations are suffering from an elevated degree of marginalization. The Cadereyta Regional Botanical Garden has developed propagation protocols of native species, and part of the stock produced will be used in the model described.

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Some of the stock of native species produced at the Cadereyta Regional Botanic Garden. Photos by Beatriz Maruri Aguilar (top) and Hugo Guadalupe Altamirano Vázquez (bottom).

At Cadereyta de Montes, some areas need a helping hand to keep the landscape in good shape. Other places hide extremely valuable living treasures that are currently struggling for survival. The Cadereyta Regional Botanic Garden is working every day to contribute to the conservation of the highly remarkable flora of the southern end of the Chihuahuan Desert, as well as to offer sustainable solutions for landscape use in a transforming environment. This way, the Garden intends to become an active participant for the achievement of Mexico’s goals for plant conservation.

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.

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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.

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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.

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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.

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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.