Here is a guest blog by RSPB's Head of Environmental Research, Dr Richard Bradbury
A recent RSPB report highlighted just what an astonishing array of biodiversity is to be found on the UKs Overseas Territories. Montserrat is one of these treasure troves, situated in the lesser Antilles island chain in the Caribbean. It’s a stunning and unusual place; home to some fantastic, and in many cases critically endangered, species that are found nowhere else. Species like the Monserrat oriole (a bird), the pribby (a plant), and the Montserrat Galliwasp (a lizard!), that RSPB and partners (Government of Montserrat, The Montserrat National Trust, Durrell Wildlife Conservation Trust and the UK Animal Health and Veterinary Laboratories) are working hard to conserve and which international visitors come to see.
Male Monterrat Oriole (Icterus oberi), by Steffen Oppel.
Montserrat hit the headlines in the mid1990s when the Soufrière Hills volcano erupted, covering the southern half of the island in ash and other volcanic debris and destroying much of the forest. Two thirds of the human population of Montserrat emigrated and the remainder now live in the northern half of the island, which is being developed. The south of the island has been declared an exclusion zone. This is putting pressure on the protected areas including the Centre Hills reserve and the protected forest, the largest intact forest area that remains, and one of the last remaining strongholds for Montserrat’s endemic flora and fauna. This is an Important Bird and Biodiversity Area (IBA) and a Key Biodiversity Area for other taxa. The threat to this important site comes from development to replace lost housing, business infrastructure and agricultural land, as well as from a more unusual source - domesticated mammals that were released during the eruption and have subsequently formed feral populations.
The Centre Hills forest on Montserrat (James Millett)
There are populations of goats, donkeys, sheep, cows and pigs. These have truly gone native and are powerful and shifty animals to be reckoned with, especially female pigs with young. Endemic plants and animals are eaten and their habitat damaged. Furthermore, where the mammals damage the native forest, it promotes the invasion of several non-native tree species (including guava) that take over the forest. Pigs disperse the seeds of the plants; storms aid their establishment by creating gaps in the forests, and the goats further help by opening up the understorey of the native vegetation. The saplings of the invasive plant species are not eaten by the livestock, as their leaves have low palatability and digestibility. These species have already naturalised in some Pacific islands where they are considered as “dominant invaders” because they spread rapidly, forming dense stands and causing severe impact on native plants.
Feral sheep on the loose in the Centre Hills forest (by Steffen Oppel)
Because of this threat to the native species, the Montserrat Department of Environment (with the help of the UK Government’s Darwin Initiative and the European Commissions BEST funding instrument, with technical support from Animal Health and Veterinary Laboratories Agency (AHVLA) in the UK) has been running a feral mammal management programme. This includes training local staff, hunting with firearms (with permission, in both the reserve and nearby parts of the exclusion zone), educating livestock owners in the surrounding area about better animal management practices, and improving a livestock tagging and registration scheme. However, long-term funding of this programme is not assured, raising concerns about the long-term future of Montserrat’s natural riches.
We investigated whether, in addition to the conservation importance of this operation, there might also be an economic argument for its continuation. We did this because it is already known that the Centre Hills are important for the ‘ecosystem services’ they provide (that is, the ‘free’ goods from nature, such as clean water, carbon storage, nature-based recreation) and it is plausible that these would be detrimentally affected by the change in the ecosystem caused by the invasive mammals.
So, we used our new toolkit for ecosystem service assessment (TESSA). The development of TESSA has been an amazing collaboration of people, from a very wide range of disciplines and backgrounds, from the Cambridge Conservation Initiative and beyond. My collaborator Dr Kevin Peh, from the University of Southampton, led the study at the Centre Hills. We examined what might happen to a range of ecosystem services (carbon sequestration and storage, provision of fresh water, nature-based tourism, as well as harvested meat from the livestock themselves) if the mammal management programme were to stop, such that the forest was taken over by non-native trees and the rare, endemic species reduced in numbers or lost.
Philemon Mapie Murrain measuring a tree in the Centre Hills as part of the carbon stock assessment (by Kelvin Peh)
The results suggest a detrimental impact on some of these ecosystem services if the feral animal control is stopped. In particular, we estimated that there could be a 46% reduction in nature-based tourism revenue associated with the Centre Hills. This was based on a survey of tourists leaving the island, which asked whether they had visited the site and how their motivation to visit the site, and spending in doing so, would change in the event of the potential change in the ecosystem. While the mammal control programme is ongoing, there is an additional benefit in terms of the supply of harvested wild meat - a benefit that would be much reduced in the absence of the control programme, due to restricted access to the mammals strongholds. Of course, with the long-term aim to eliminate the mammals completely, then this benefit would reduce over time. And theses benefits are without accounting, for instance, for any potential impacts of wandering feral animals raiding crops or colliding with motor vehicles.
This study suggests that there are some economic benefits to the feral livestock management programme in Montserrat, as well as the conservation benefits. But how might the potential tourism benefit be made real? One option might be some form of modest tourism or green visitor exit tax in a carefully managed dedicated fund. But, lessons learned from schemes in other Caribbean UKOTs indicate that a very robust mechanism for distribution of green tax revenue needs to be in place from the outset of any proposed scheme.