By Eva Colberg, postdoctoral fellow at Cornell University. Nearly all of Mauritius’s contemporary conservation plights are rooted in or exacerbated by the effects of invasive, non-native species. To see what restoration can do for the island’s few remaining forests, Dr. Eva Colberg joined members of the Tropical Island Biodiversity, Ecology & Conservation research group to visit (and weed) one of the island’s forest restoration sites.
Red stems of strawberry guava (Psidium cattleyanum) form a wall dense enough to prevent walking through most of Mauritius’s remaining forests. Beyond impeding movement, the thick guava understory also reduces overstory tree fitness and disrupts native forest growth and succession. Originally from South America, strawberry guava is a classic case of a non-native, invasive species outcompeting and reducing habitat quality outside its native range (and islands are particularly vulnerable to invasion).
The ongoing onslaught of invasion means there’s no time to waste for restoration ecologists like F.B. Vincent Florens, Associate Professor at the University of Mauritius. “We have so many rare species on the brink of extinction [over 80% of the island’s endemic flowering plants are threatened], and have to work at the same time and learn as we go.” His life experience and ecological studies point to invasive species management as the island’s best hope for restoration and conservation, which he likens to healthcare. “First you save the person from dying and then you can treat the other issues.”
Despite decades’ worth of evidence pointing to the efficacy of invasive plant removal in Mauritius, it still isn’t widely implemented. Less than 5% of the island’s few remaining forests have been weeded of invasive plants, and even the best-protected forests are already dominated by invasive undergrowth. Frustratingly, some of the resources that could be used for invasive removal have instead hindered restoration via removal of native pioneer and nurse tree species. “We can do a lot of science, can come up with a lot of facts, but how do we get people to do what they don’t want to do?” Indeed, it’s far easier to uproot a small plant than to change someone’s mind, and Prof. Florens has an entire country to convince that saving their native forests is not only possible, but worth the effort.
Leighton Reid describes new research linking slow forest recovery to the ancient and protracted isolation that has made Madagascar a hotspot of global endemism – plus an example of working with local farmers to overcome these challenges and restore native rain forest.
Madagascar is a special place with a special history. Separated by ocean from Africa and India for the last 88 million years, this isolated tropical island has fostered the evolution of plants and animals found nowhere else on Earth. Lemurs, couas, and the plant family Sarcolaenaceae are all examples of organisms that evolved only in Madagascar. Collectively, such endemic species make up more than 80% of all plants and animals there.
Madagascar also has special problems. Almost half of the island’s forest has been cleared for agriculture since 1953, and remaining forests are at imminent risk. One recent study projected that if deforestation rates do not diminish soon, 93% of eastern Malagasy rain forest could be gone by 2070.
The combination of a large proportion of endemic species and a high degree of habitat loss makes Madagascar a biodiversity hotspot. Some people call Madagascar one of the hottest hotspots because its endemism and habitat loss are so extreme.
This week, a new study led by UC Berkeley PhD student Kat Culbertson identified another special problem in Madagascar: following disturbance, Malagasy forests recovery very slowly. Compared to other tropical forests around the world, Malagasy rain forests recover only about a quarter (26%) as much biomass in their first 20 years of recovery. Dry forests in Madagascar also recover more slowly, recovering just 35% as much biomass as American tropical dry forests over the same time period.
Why do Malagasy forests recover more slowly than forests in other regions? The answer may be related to Madagascar’s unusual evolutionary history. Culbertson and her co-authors developed four hypotheses and reviewed an array of scientific literature to evaluate support for each one.
Four ways that Madagascar’s unique history could lead to slow forest recovery
1. Native Malagasy forests lack resilience to shifting nutrient and fire regimes from current farming practices.Many rural people across Madagascar practice tavy, a farming method that involves clearing forest, burning it, and then growing rice – a staple crop. After one or a few years of growing rice, the land is allowed to recuperate for several years before it is cultivated again. In other tropical forest locations, such as southern Mexico where humans have farmed for thousands of years, similar practices can coexist with native forests, but Malagasy forests seem to have little resilience to tavy, as least at the intensity with which it is practiced today. For example, in eastern Madagascar, a 3-5 year tavy cycle can cause a native forest to transition to permanent herbaceous vegetation in just 20-40 years. The soil nutrient stocks in that fallow field may be as little as 1-6.5% of soil nutrients stocks in intact forest.
2. Madagascar is an island, and islands tend to have more problems with invasive species. Goats in the Galapagos, brown tree snakes in Guam, acacia in Hawaii, and rats everywhere – these are just some of the ways that island ecosystems have been overwhelmed and transformed by invasive species. Madagascar is no exception. Rain forest regeneration at Ranomafana is stalled by invasive guava, eucalyptus, and rose apple, while dry forest regeneration at Berenty is inhibited by a vine – Cissus quadrangularis. People in Madagascar have many more anecdotes about problems with invasive species like silver oak and Melaleuca quiquenervia, although the extent and impact of these invaders on forest recovery have not yet been studied.
3. Old, weathered soils have favored the evolution of slow-growing native plants. Madagascar is not only an island, it is a very old island, and as such its soils have been weathered and depleted of important nutrients like phosphorus. It’s hard to separate the effect of inherently low nutrient availability due to being an old island from the effect of human-induced nutrient scarcity through tavy, but one comparison of phosphorus content in rice stalks showed that phosphorus content was 10× lower in Madagascar compared to the rest of sub-Saharan Africa. If native trees have evolved to grow more slowly in Madagascar because of low nutrient availability, then on average exotic tree species should grow faster than native Malagasy ones in the same gardens. This has been shown in a few cases, but a more compelling analysis would need more species.
4. Finally, Malagasy forests have dysfunctional seed dispersal. One way in which Madagascar is different from other tropical areas is that by and large its trees have evolved to have their fruits dispersed by lemurs. Unfortunately, many of the lemurs that could disperse Malagasy tree fruits are either extinct or endangered – in many cases due to a combination of hunting and habitat loss. Moreover, the lemurs that remain are reluctant to venture outside of forest fragments (perhaps with good reason) and so they are unable to disperse seeds to regenerating farmlands that most need them.
In essence, the ancient and protracted isolation that has made Madagascar so unique has also made it uniquely vulnerable to contemporary changes like deforestation, fire, and agriculture. The result is an unfortunate combination: Madagascar not only has some of the highest deforestation rates, it is also one of the places least ecologically equipped to rebound from those disturbances.
The way forward – working with local people
Despite these challenges, Madagascar has committed to restoring four million hectares of lost habitat by 2030, an area nearly 7% the total national territory. This is a tall order in a country where technical difficulties are high and financial resources are often low, but it can be done, and the way forward, undoubtedly, is to work with local people.
One group that exemplifies bottom-up restoration is GreenAgain, a non-profit restoring native rain forest and supporting rural livelihoods in eastern Madagascar. GreenAgain is led and staffed by farmer-practitioners whose neighbors, family, and friends contract with GreenAgain to design, plant, and monitor diverse native forests on their lands. Last year, GreenAgain staff planted 20,000 trees across central eastern Madagascar, each one carried by hand, on foot, from one of eight regional tree nurseries. The rural farmers at GreenAgain collect rigorous data on tree survival and growth and collaborate with scientists to analyze and share the results of their tree planting experiments.
For example, one of the earliest experiments at GreenAgain was an assay of tree planting strategies intended to improve native tree seedling survival during plantings that occur in the dry season. Trees planted during the dry season typically have high mortality, sometimes in excess of 40%. One of the strategies that local farmers recommended to improve survival was to erect small teepees over each seedling using the leaves of a common fern, Dicranopteris linearis. These structures are temporary – they eventually dry out and blow away – but GreenAgain’s experiment showed that they reduced transplant shock (i.e., mortality in the first few weeks) by 75% compared to seedlings that were left to bake in the hot sun. In contrast, many of the other treatments had no discernable effect.
To analyze and publish these findings, GreenAgain partnered with an award-winning undergraduate researcher, Chris Logan, in my lab at Virginia Tech, who led a peer-reviewed paper that is now available at Restoration Ecology.
Could technological solutions like hydrogels or irrigation systems produce greater improvements in dry season tree survival? Yes – they probably could for a certain price, but homegrown solutions like fern leaf shade tents are free and easily accessible to any person doing restoration across eastern Madagascar. They are also more likely to be used because they were developed by local people.
This study also showed that some native tree species are much better at coping with dry season stress than other species, so another possible solution for dry season plantings could be to plant only the tough survivors. Once those trees survive and begin to produce shade, fern leaf tents may not even be needed anymore to help more sensitive native species survive and grow.
To read more about ongoing restoration and ecological research in Madagascar, read our new review of how Madagascar’s evolutionary history limits forest recovery and our new open-access paper about strategies for dry season plantings in eastern Madagascar.
If you are in a position to support the work of local farmers restoring rain forests in eastern Madagascar, consider donating to GreenAgain at their website, greenagainmadagascar.org.
By Thibaud Aronson and James Aronson. All photos by Thibaud Aronson.
The main island of Madeira is just 740.7 km2 (286 mi2), while the handful of others are rather barren, and mostly uninhabited. That means the entire Madeiran archipelago is about the size of a medium-sized National Park in the US, such as Crater Lake, in Oregon, for a total population of just over 250,000.
For garden and natural history/cultural history-oriented travellers, Madeira and its neighbors – the cooler Azores to the north, and the drier Canary Islands – are spectacular: these are three of the most appealing areas of the Atlantic for human habitation, gardening, farming, and hiking, with floras and faunas related to European, Mediterranean, and African biota, as well as some unifying Macaronesian elements shared among the three archipelagos. Agricultural crops are also quite spectacularly varied, with a strong presence of vineyards of very stunning appearance, and also subtropical bananas (about which, for some history, including the tale of the EU’s “bendy banana law”, see here).
Of particular interest on the island – of combined natural and cultural heritage value, are the laurel forests (laurisilva to botanists). Mostly dominated by evergreen trees and tall shrubs of medium stature – no more than 15-20 m high – these kinds of forests typically occur at subtropical latitudes, in areas with mild climate and high humidity. They can be seen – in unconnected fragments for the most part, and with varying botanical composition of course – in places such as the Himalayan foothills, central Chile, or the highlands of Ethiopia. In Europe, true laurel forests used to cover much of the Mediterranean basin during the Tertiary era, from which they receded and disappeared as the region’s climate got progressively drier. Apart from a few fragments left in the remote Anti-Atlas Mountains of Morocco, and one small patch in southern Spain, the only surviving Atlantic laurel forests are found in Macaronesia. The highlands of Madeira hold the largest and best-preserved stands, somewhat protected over the past six centuries by the island’s dramatic topography and, since 2009, thanks to recognition as a UNESCO World Heritage site covering 15,000 hectares.
Madeira’s laurisilva is draped in mist more often than not, and exuberant lichens and ferns cling to every tree branch, giving these forests a very primeval feeling, unlike anything else in Europe. The forest type is dominated by under a dozen evergreen tree species, most notably laurels (5 species in 4 different genera of Lauraceae) and tree heaths (Erica spp.), some of which get to be exceptionally tall for Ericas. But there are several dozen endemic shrubs and herbs in the undergrowth, such as various Geraniums and several giant daisy relatives. It has three endemic bird species as well.
The archipelago was uninhabited until Portuguese sailors claimed it for the Portuguese crown in 1417. The island’s appealing climate was not lost on them and they set about settling it. Much of what they did shaped the island that we know today and no doubt led to a massive amount of irreversible clearing, deforestation, and soil erosion, as we will discuss further on.
Madeira’s climate is very unbalanced. The northern slopes can receive nearly 3000 mm of rain in a year, while the southern part of the island is much, much drier. However, the south has gentler slopes, making it much more suitable for building and agriculture. Therefore, the Portuguese set about building levadas, irrigation canals to bring water from the north to the south. This enormous network, spanning thousands of kilometers, much of it dug from sheer cliff faces, with numerous long tunnels as well, was built over four centuries (with slave labor, many of whom lost their lives in the process); without it, large-scale settlement of Madeira would have been near impossible.
The island also achieved tremendous prosperity especially in the 17th, 18th and 19th centuries, thanks to its privileged position for maritime trade in the north Atlantic and, for a while, its role as one of the world’s largest sugar cane exporters. The richer inhabitants, taking advantage of the favorable weather, began a tradition of having extravagant gardens, with plants from all over the world. Indeed, a walk in the streets of any town on the island today will reveal gardens bursting with an incredible melting-pot of plants, with Hydrangeas (from east Asia), growing side by side with Agaves and Yuccas (from Mexico), Agapanthus (from South Africa), Brugmansias and Passionflowers (from the Andes), Bougainvillea from the South Pacific, and more marvels, all under the shade of massive Agathis and Eucalpyts (Australia) and Araucaria trees (Norfolk Island, and Chile)! There is perhaps no better illustration of this potpourri quality of the cultivated plants than the fact that Madeira’s official flower is the Bird of paradise, Strelitzia reginae, a native of… South Africa!
However, to anyone with naturalist’s eyes, a lot of what is seen outside of gardens is quite worrisome when one considers the island’s native flora, fauna, and varied ecosystems outside of the protected areas where the laurisilva occurs. There are massive areas of soil erosion, and as elsewhere throughout the Mediterranean region, abandoned lands and pastures that appear to have been cleared and then repeatedly burned over several centuries to maintain grazing lands for sheep and goats. Most of the extant revegetation has been done with Eucalyptus globulus, Mediterranean pines, and various other non-native conifers and Australian Acacias. Of these latter fast-growing, colonizing, bird-dispersed trees, at least 6 are invasive on Madeira and the Azores, the worst of the lot being Australian blackwood.
So what now, from a restoration ecology perspective? Madeira is subject to strict Portuguese laws regarding sale or import of known invasive plant species; this makes a lot of sense given that already 15% or more of the flora of Portugal, and probably more than that in the Azores and Madeira consists of non-native invasives. But a lot of work beyond protection against new invasions could be envisioned, starting with control or eradication efforts on such an island whose natural beauty and biodiversity are its greatest asset. Reintroduction and reinforcement of populations of endangered native species are also needed and initial experiments in ecosystem restoration could be undertaken on the main island and perhaps some of the smaller islands as well. Education and job training and greater funding for restoration work are all needed and would probably be of great, and lasting value to local communities and the Autonomous Region as a whole. Coordination with similar efforts in the Azores, and on the mainland territory of Portugal should all be encouraged.
One invader to be carefully monitored on Madeira is Kahili Wild Ginger (Hedychiumgardnerianum) a garden-escape that is known to do great ecological damage to native woodlands in Hawai’i, and elsewhere. The IUCN considers it to be one of the world’s 100 worst invasive species. Indeed, its 1.5 to 2 m tall stalks can form extensive stands, with dense mats of rhizomes, that can choke out native understory if left unchecked. Reportedly, control efforts are underway inside the Madeira Natural Park.
But what about all the areas infested with woody weeds outside the parks and UNESCO Heritage sites in the mountains? From our point of view, the extensive and multiplying stands of Acaciamelanoxylon and other invasive wattles (Australian acacias), of Gorse (Ulexeuropaeus) and a few other noxious woody weeds we saw plenty of, it seems clear that manual and mechanical controls, and perhaps some biocontrol would be worth testing.
And, what about everything that ecological restoration, sensu lato, could bring to Madeira? On one road, in the center of the country, we saw a rather large plantation of tree saplings that looked like Ocoteafoetens, one of the five native laurels of the laurisilva. That was encouraging to see, but the trees were planted grid-fashion and in monoculture, so that it was unclear what the intention was. As readers of this blog well know, reintroduction (or reinforcement of populations) of a single species of native plant or animal is not the same thing as ecological restoration: ‘restoration of Ocotea foetens’ is a non sequitur whereas reintroduction of this native tree, or its use in reforestation does make sense.
We also learned that studies are underway regarding the native olive tree, long considered a feral ecotype or, for some systematists, a subspecies of the widespread European olive, Olea europaea, but now generally accepted as an island endemic Olea madeirensis. Pride in such native species should be definitely encouraged, serving as a driver for more attention to what should be planted in the context of future ecological restoration programs in coastal areas and hills, and in environmental education programs, parks, and botanical gardens as well.
Next, let’s consider the spectacular Dracaena draco, or Dragon tree, that prospered on Madeira and also in the Canary Islands, Morocco, and Cape Verde, until Europeans in the 15th and 16th century began aggressive tapping of the sap from this stem succulent tree – the so-called Dragon’s blood – which was widely prized as a durable natural dye. By the end of the 16th century, Dragon tree was rendered nearly extinct in its natural distribution area thanks to a typical boom and bust pattern of exploitation, and today, the only wild populations of any importance occur on Tenerife, in the Canary Islands, with a few individuals in Morocco and Cape Verde.
This iconic tree is seen planted all over Madeira, and indeed in frost-free dryland gardens all over the world. But there probably isn’t a single wild dragon tree left on the island! So, what should attempts to restore an ecosystem with populations of Dragon tree look like, over and beyond reintroductions? What reference should be used and which provenances of what trees should be planted and what else is needed for the project to survive and be meaningful to Madeirans?
And now, for our last snapshot, let’s consider the Foxtail Agave, that is widely planted and clearly spreading on coastal cliffs and hills in Madeira. It is an absolutely stunning plant, and of great natural history interest but it starting to naturalize, following in the pattern of Agave americana and Opuntia stricta, that could already be considered serious weeds. Local people probably don’t consider that a problem, and we can certainly understand that, given the newcomer’s graceful beauty. But like the Kahili ginger, and the widely planted Aloe arborescens, the Foxtail Agave is a serious pest on O’ahu and other Hawai’ian islands, and this should give cause for concern to Madeirans.
But, then, who are we to say what attitude Madeirans and their authorities should adopt towards non-native invasives? Given the fact that tourism is now far and away the leading economic sector on the island, perhaps – like the Galapagos Islands, or Iceland, or Malta – greater sensitivity to the need for and the value of ecological restoration efforts will develop in the future.
One thing we could offer is a reminder that ecological restoration clearly includes restoration (or ecological and economic rehabilitation) of cultural or semi-cultural ecosystems, not to mention social-ecological systems and cultural landscapes. In the case of Madeira, this line of thinking would allow for reflection, and encourage investment in the restoration and rehabilitation of the working landscapes that thrived in lower latitudes on the southern half of the island with irrigation water being provided from the levada networks in the mountains. We can imagine remarkably interesting and inspiring landscape-scale restoration with ample opportunities for agritourism, and an expanded form of nature-based or ecotourism that would include cultural landscapes and heritage crops and traditional livelihoods, developed along corridors and valleys connecting levada canals all the way down to restored ‘working landscapes’ that certainly could have multiple benefits for local communities, for biodiversity, and for an emerging restoration economy linked to tourism. Worth considering, no?
Aotearoa New Zealand’s biodiversity has a unique story
Indigenous biodiversity in Aotearoa New Zealand is in dangerous decline – this is not a unique situation on the world stage. However, the story of how we got to this point and our planned approach towards recovery could be perceived as rather novel.
Our biogeographical story
The fascinating islands of Aotearoa New Zealand have been isolated in the Pacific Ocean for up to 80 million years. The islands are long and narrow, straddling latitudes from 34° to 47° south and encountering climates from subtropical in the north to subantarctic in far south. The country experiences a highly changeable climate that is coupled with wildly variable geographic features. In Te Ika a Māui – the North Island, landscapes range from white sandy beaches to active volcanoes and rugged western coast lines. While in Te Wai Pounamu – the South Island, you can encounter temperate rainforests, dramatic glacial fjords, dry open plains as well as the rugged Southern Alps.
This isolation, habitat and climatic variability in an island context has influenced the evolution of unique indigenous flora and fauna with a high degree of endemism (100% of frogs and reptiles, 90% of insects and approximately 80% of vascular plants) and a particular fragility and vulnerability to predation and competition from invasive non-native plants and animals.
New Zealand’s National Science Challenges
Despite extensive reporting on biodiversity decline in Aotearoa New Zealand, an effective approach for reversing the loss of our special indigenous species has not been identified. This is where the National Science Challenges come in.
Established in 2014 by the New Zealand government, the 11 cross-disciplinary, mission-led National Science Challenges are working to address science-based wicked problems that researchers and residents are most concerned about. The Science Challenges focus on many aspects of society, the natural environment, the urban environment and economic development. They involve collaboration between universities, other academic institutions, crown research institutes, businesses and non-government organisations. Together, the Challenges will receive NZ$680 million (US$491.5 million) of government funding over ten years.
Biodiversity and biosecurity are central for New Zealand’s Biological Heritage National Science Challenge | Ngā Koiora Tuku Iho (or, ‘BioHeritage Challenge’ for short). The BioHeritage Challenge is focussed on discovering the most effective means of protecting and managing native biodiversity, improving biosecurity and enhancing resilience to harmful organisms. This work is centred on three core goals and is grounded in strong values that embrace partnerships with Māori (indigenous peoples of Aotearoa New Zealand):
Introducing the Eco-index programme
The Eco-index programme is one of 14 research teams in the BioHeritage Challenge. With a focus on the Whakamana (Empower) goal, the Eco-index team is thinking outside the square to measure and direct land managers’ investment in ecological restoration.
Aotearoa New Zealand has a significant evidence base that biodiversity decline is occurring, but an effective countrywide approach to reverse this trend has not eventuated. A team of national and international experts from many different fields spent 6 months developing our novel Eco-index approach to address this issue and specified a starting with the formation of a long-term biodiversity vision, followed by a means of accomplishing the vision.
Eco-index 100-year national vision for biodiversity restoration
To guide long-term change, the Eco-index programme has developed a 100-year national vision that is informed by the targets, perspectives and strategies of biodiversity stakeholders across our nation, including iwi (Māori tribal groups), businesses, communities, NGOs, primary industries and governmental organisations.
The resulting shared vision for Aotearoa New Zealand is based on thriving, ecologically robust corridors of indigenous landcover that stretch from mountains to the sea. These biodiverse corridors will link our conservation estate with private and production landscapes and contribute to 15% of original ecosystem extent being restored, protected and connected in every catchment.
To contribute to methods for development of national restoration visions internationally, we are in the process of publishing our vision creation methodology in the primary literature.
Achieving the vision: linking biodiversity investment with impact
The Eco-index programme is utilising existing big data to quantify investment that land managers of all types are making to benefit indigenous biodiversity. These investments include restoration practices like native plantings, control of non-native invasive mammals (e.g., rats and stoats), protection of indigenous ecosystems, and planning work that goes into all of these. We are then linking this investment with big data indicating the impact these investments have on biodiversity. These data include indigenous species increases or decreases, especially those of importance to Māori, indigenous landcover, and human-nature connectedness. These links will be made at national, regional, iwi (Māori tribal groups) and industry scales and will provide:
an overall score of Aotearoa New Zealand’s biodiversity status updated regularly and shown at different scales, therefore showing trends over time;
biodiversity impact comparisons between industries and trends over time;
determine overall investments needed for effective biodiversity restoration by key land managers (e.g., government, industries, iwi, NGOS);
determine correlations between levels of investment in biodiversity restoration and levels of impact on biodiversity status nationally, regionally, and across industries;
identify best or most effective biodiversity protection and restoration investments by major region and industry.
How is the Eco-index approach novel?
Our point of difference is that we are co-designing with key land managers across the country to understand what will help them most. A large proportion of indigenous ecosystems in Aotearoa New Zealand is on privately-owned agricultural land and many land managers are passionate about protecting and enhancing indigenous biodiversity but need to know best actions to take. Our programme will identify the most effective incremental investments that land managers (including iwi), as well as investors and communities, can make to generate the cumulative intergenerational impact needed to reverse decline. Creating and tracking this change using the Eco-index outputs will enable an effective, collective journey.
In time, the Eco-index will indicate our Aotearoa New Zealand’s biodiversity performance, much like GDP indicates economic performance.
Current Eco-index focus – June 2021
The Eco-index programme runs from 2020 to 2024. We are building relationships with key land managers and data owners to co-design our approach and discover efficient ways to work together for the benefit of indigenous biodiversity. We are also developing methodology for gathering and analysing relevant biodiversity investment and impact data. The application of fast-evolving artificial intelligence and machine learning technology may be the key for cost-effective analysis of existing big data and satellite imagery across Aotearoa New Zealand.
About our team
We have expertise in Aotearoa New Zealand ecology, economics, sustainable development, land management systems and ecological restoration. The Eco-index team is led by Dr. John Reid (Ngāti Pikiao, Tainui, JD Reid Ltd.) and Dr. Kiri Joy Wallace (Te Pūtahi Rangahau Taiao – Environmental Research Institute, University of Waikato).
Keep up to date!
Interested in the Eco-index programme? See more at www.eco-index.nz and like/follow us on Facebook and Twitter to be updated on our progress and discoveries:
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.
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.
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.
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.
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.
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.
Oban, the only settlement on Stewart island. Walk in any direction out of town, and you quickly find yourself entering the surrounding national park.
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.
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.
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!
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.
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.
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.
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.
Octavian Grigoriu setting possum bait laced with cyanide in his privately-owned forest reserve.
Leighton Reid, a postdoctoral fellow in the Center for Conservation and Sustainable Development, reflects on tortoises, tree cacti, and ecological isolation.
The Galápagos is the world’s most pristine tropical archipelago, and it is utterly unique. Nearly the entire island group is a national park, and 200,000 visitors per year come to witness its ecological singularities ‒ things like penguins and iguanas swimming side-by-side through a mangrove lagoon. The archipelago consists of fourteen large, volcanic islands and over a hundred smaller rocks and islets. Most of the land surface is low and dry. The easternmost island is about 900 km from mainland Ecuador, which is a probable source for the organisms that first began to colonize Galápagos when its volcanic peaks surfaced above the Pacific five million years ago. Indeed, the islands’ ecology is characterized by their isolation. Each island contains a relatively low diversity of organisms, many of which are unafraid of large primates. The biotas’ ecological simplicity and naiveté have facilitated major scientific discoveries, such as that small, heritable variations can have life or death consequences for individuals and ultimately change populations.
One of the more bizarre life forms on Galápagos is the tree cactus. Prickly pear cacti (Opuntia species) are not particularly rare in the western hemisphere. In the United States, for instance, they occur in every state except Alaska. But over millions of years in Galápagos they have become quite varied. Some grow low to the ground, like the familiar continental forms, whereas others grow as trees, towering up to 15 m above the ground. The first botanist to speculate on this phenomenon was Alban Stewart (1911), a scientist-sailor with the California Academy of Science. He noted that erect, tree cacti tended to grow on islands that also housed another over-sized organism – the Galápagos tortoise (Chelonoidis nigra). Galápagos tortoises eat the fleshy cactus pads, which contain water – a limiting resource in arid environments. Stewart posited that the pressure from tortoises craning their long necks upward to munch cactus pads may have favored taller cacti.
Opuntia echios var. barringtonensis is one of the taller tree cacti, presumably made that way by pad depredation by giant tortoises over many generations.
A low-growing cactus (Opuntiaechios var. zacona) growing on Seymour Norte, an island that historically had no tortoises or iguanas. Herbivore pressure is visible here; an introduced land iguana (Conolophussubcristatus) has been taking bites from the lowest pads.
The relationship between tortoises and cacti was thrown into disarray after the Galápagos were discovered (accidentally) by Panamanian Bishop Tomás de Berlanga in 1535. By the late 19th Century, pirates and whalers removed thousands of tortoises from the islands, stowing the living animals in their holds as fresh meat for their long Pacific voyages. Eventually, overharvesting extirpated tortoises from several of the islands, with rippling effects on the rest of the ecosystem. Even where tortoises survived, they were often unable to reproduce because their offspring were eaten by introduced, European rats. Tree cacti were among the hardest hit; tortoise decimation stripped these plants of their main seed disperser.
Reintroduced giant tortoise in the littoral zone on Isabela Island.
In response to tortoise declines, the Charles Darwin Foundation and the Galápagos National Park Service began a captive breeding program on Santa Cruz Island. Since 1965 they have raised and repatriated thousands of tortoises to several islands, waiting to release them until the tortoises have gotten big enough to be “rat proof”. By and large the reintroductions have been successful. On Española Island, for example, tortoise populations had crashed to fifteen individuals in 1960, but by 2007 more than 1500 individuals had been repatriated, and the population appeared stable. Moreover, these reintroduced tortoises reinitiated seed dispersal for an endangered tree cactus (Opuntia megasperma var. megasperma), increasing the number of juvenile plants.
In addition to species reintroductions, ecological restoration in Galápagos has often entailed species eradications. Isolation historically shaped Galápagos ecology; nine hundred miles is a long way for a snake or a lizard to float on a vegetation raft. But Galápagos’s isolation was compromised by seafaring humans, who facilitated island colonization by domesticated animals and hundreds of plant species. Goats have been among the worst invaders. Until recently, goats overgrazed the islands’ vegetation, converting it into habitat unsuitable for native species. One of the most ambitious restoration projects in Galápagos has been eradicating goats from the archipelago. On the largest island, Isabela, more than 140,000 goats were killed in 2004-2005 using unconventional restoration tools, including helicopters, AR15 rifles, and Mata Hari goats – sterilized female goats induced into long-term estrus and fitted with radio telemetry collars to root out the last hold-outs. Goat eradication has resulted in spontaneous vegetation recovery. In addition to goats, the Charles Darwin Foundation and the Galápagos National Park Service have also eradicated eight exotic plant species. Other species will be harder to get rid of, like rats, guava, blackberry, and domestic cats.
Despite its one-of-a-kind nature, can the world’s most pristine tropical archipelago serve as a reference for other arid, tropical islands? That is, can we evaluate the success of other island restorations by comparing them to the relatively intact Galápagos’s ecosystem structure, function, and composition? Perhaps to some extent we can. Historical contingency leads to unique island assemblages (for example: giant tortoises in Galápagos, giant skinks in Cabo Verde, giant lizards in Komodo), but many islands may be characterized by their lack of functional redundancy. In other words, if you remove a species from an island, the ecosystem consequences may be greater than if you had removed a species from a more diverse mainland ecosystem. Additionally, plant restoration in the arid Galápagos suggests that when disturbances are removed, vegetation can recover rapidly. This may also be true of other oceanic archipelagos, whose plants and animals have already colonized difficult terrain from a long way away.
Land iguana and tree cacti (Opuntia echios var. echios) on Plaza Sur Island.