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BVI Mangrove Rapid Assessments Preliminary Report

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Abstract and Figures

In response to the devastation of this fragile coastal habitat, a series of rapid mangrove assessments were conducted in the British Virgin Islands with logistical support from the Jost Van Dykes (BVI) Preservation Society and sponsored by regional wildlife organization, BirdsCaribbean in April 2018. The purpose of these assessments was to characterize the post-hurricane status of the mangroves of the BVI. Baseline data obtained will be used as a starting point to develop preliminary recommendations for conservation and restoration needs and priorities for the Territory for the future.
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Mangrove Rapid Assessments Post-Hurricane Irma:
Preliminary Results and Recommendations for the British Virgin Islands
University of New Hampshire
Prepared for:
Suzan Zaluski
Jost Van Dyke Preservation Society
Prepared by:
Gregg E. Moore, Ph.D.
Jackson Estuarine Laboratory, 85 Adams Point Road, Durham, NH 03824
gregg.moore@unh.edu
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PELIMINARY REPORT on EXISTING CONDITIONS:
MANGROVE RAPID ASSESSMENT POST-HURRICANE IRMA
PRELIMINARY RESULTS AND RECOMMENDATIONS FOR THE BRITISH VIRGIN ISLANDS
On the cover: Defoliated red mangroves (Rhizophora mangle) of Deep Harbor, Virgin
Gorda, BVI hiding a wealth of naurally recruited seedlings among its
tangled roots. Photo by G.E. Moore.
Cite as: Moore, G.E. 2018. Mangrove rapid assessments post-Hurricane Irma
Preliminary results and recommendations for the British Virgin Islands. Technical Report
prepared for the Jost Van Dyke Preservation Society, BVI.
G.E. Moore, Ph.D. 2018
gregg.moore@unh.edu
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Introduction
Mangroves are the dominant coastal vegetation of low energy coastal areas in the Caribbean. Salt tolerant
plants that grow in or near the water’s edge, mangroves provide countless benefits to nature and humans.
Mangroves provide habitat and nursery area for fish, playing an important role in fishery and coral reef
health. Additionally, they support water quality by providing a catchment for upland run off and buffer
storm surge, wind and waves, protecting coastlines. Despite their importance, mangroves are globally
threatened by land development, pollution, natural disasters, and the various effects of climate change.
Despite global declines (or perhaps in part because of it), awareness of the importance of mangroves and
the ecosystem services they provide are growing. Grass roots organizations, NGO’s and the governments
of many nations are strengthening strategies to protect these systems, including an increase in Marine
Protected Areas and associated land and ocean management planning.
Even with heightened government and regulatory protection, the increasing frequency and intensity of
coastal storms remain a significant threat to the resiliency of mangroves. On September 7, 2017,
Hurricane Irma made landfall in the BVI. Noted as the most powerful Atlantic hurricane ever recorded,
with winds that averaged 185mph, gusting to 215mph, the super-storm caused extensive destruction to
homes, buildings, infrastructure and the natural environment. Less than two weeks later, the islands were
hit for a second time by Hurricane Maria. Among the natural habitats hardest hit was the coastal fringing
mangrove (Figure 1).
Figure 1. Aerial view of storm damaged fringing mangrove forest from Bakers Bay, Jost Van Dyke,
representing the dominant condition throughout the Territory (Photo date: April 8, 2018).
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In response to the devastation of this fragile coastal habitat, I carried out a series of rapid mangrove
assessments in the Territory with logistical support from the Jost Van Dykes (BVI) Preservation Society
and sponsored by regional wildlife organization, BirdsCaribbean during the week of April 8, 2018. The
purpose of these assessments was to characterize the post-hurricane status of the mangroves of the BVI.
Baseline data obtained will be used as a starting point to develop preliminary recommendations for
conservation and restoration needs and priorities for the Territory for the future. As the BVI was only one
of many Caribbean countries impacted by these 2017 Hurricanes, this work will contribute to an
overarching goal of examining the impacts and related coastal resiliency planning needs for the affected
region as a whole.
Study Area and Methods
Site visits were completed on Jost van Dyke, Tortola, Frenchman’s Cay, Beef Island, Great Camano, Virgin
Gorda and Prickly Pear Islands (Figure 2). Due to the area that was to be covered and limitation of time,
the majority of rapid assessment observations were conducted from the seaward edge (by boat), while a
subset of sites was visited by car. Unmanned Aerial Vehicle (drone) based aerial surveys were conducted
in some locations. At all sites, I documented the dominant status of the mangrove (live/dead), noted
recruitment potential (seedlings or propagules present/absent), and noted if dead trees had been
cut/cleared. Where live, mature plants remained, the canopy height was visually estimated, and an
approximate density estimate was noted.
Figure 2. Study area for rapid mangrove assessments in the BVI (April 2018).
Results and Discussion
The rapid assessment confirms anecdotal reports of extensive mangrove loss in the BVI. Based on my
observations, roughly 90% of all the mature red mangrove trees that form the coastal fringing system
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have been defoliated appear to be dead, exhibiting little to no new growth (Figure 3). The sub-canopy,
when present, was also badly impacted and easily 50-70% of the pre-storm shrub layer has also been
damaged, defoliated and unexpected to recover. The significance of these findings is that the systems’
natural ability to recolonize has been severely impacted since the storm damage resulted in loss of mature
plants that would produce the flowers and fruits needed as the source of the next generation(s) of
mangroves. As a result, successful regeneration of the forest is primarily dependent on the rooted
seedlings that are found in scattered, mixed density patches on the forest floor. Fortunately, there are
some exceptions, particularly in more sheltered locations such as the inner lagoon of Paraquita Bay in
Tortola, portions of Bluff Bay on Beef Island and Biras Creek in Virgin Gorda (Figure 4). In the latter case,
the remaining mature plants were predominantly shrubs occurring beneath the original forest canopy,
yet they are capable of bearing flowers and producing propagules the region so desperately needs.
Figure 3. Examples of fringing mangrove impacts that are typical throughout the Territory.
Figure 4. Surviving plants remain in isolated protected locations in the mangrove at Beef Island’s Bluff Bay
(left) and shorter shrubs (2-3m) spared as forest canopy was stripped out by back-to-back storms in Virgin
Gorda (right).
From a distance, it would seem that the prognosis for the BVI’s mangrove is quite poor. Fortunately, the
closer one gets to these storm-wracked forests, the more it seems there may be some hope for resilience.
Patches of freshly rooted propagules (seedlings) trapped among the tangle of dead prop roots beneath
the former mangrove forest abound in some locations (Figure 5). These were often situated inland from
the water’s edge and difficult to see without accessing the mangrove interior. Since very few mature, fruit
bearing trees remain after the devastation of the storms, these ‘seedling groves’ singularly represent the
future of the mangrove forest for the BVI for many hard-hit locations in the Territory. It is possible that
G.E. Moore, Ph.D. 2018
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these sites hold potential for sustainable recruitment of plant stock for restoration and conservation
efforts for BVI’s future, but it will be years before these fragile seedlings reach maturity and bear new
recruits themselves.
Figure 5. Encouraging examples of dense understory seedlings springing forth from the now open canopy,
noted at many locations throughout the rapid assessment sites.
Table 1 summarizes general observations made at select observation points during the rapid assessments.
Note these represent observations at points within each system in an attempt to characterize the overall
condition at each. Further quantitative field measures would be required to fully assess these mangroves
and to initiate a statistically robust data set for study, ecological monitoring, or development of applicable
conservation and restoration efforts.
Table 1: Summary of rapid assessment observations at select mangrove sites in the Territory.
In addition to the storm damage, I noted additional impacts at some site. It is clear that dead wood had
been cut flush to the prop roots in some locations, particularly in Virgin Gorda and Frenchmans Cay. It
Canopy Subcanopy Canopy He ight Density Recruits
Island Site Name (Live/Dead) (Live/Dead) (m) (estimated) Yes/No Comm ents
Beef Island Bluff Bay 1 (interior) Dead Live 330% yes Canopy damaged, understory survived, recruits many
Bluff Bay 2 (interior) n/a Live 215% yes Protected area w s cattred shrubs, flowering and recruits
Bluff Bay 3 (fringe) Dead Live 210% no* Larges t trees observed, all dead; scattered shrub and recruits
Frenchmans Cay Cause way De ad Dea d <1 <1 no Clea rcut to prop root s; l ittle to no recrui ts obs erved
Great Camano Cam Bay Dead Dea d <1 <5% no Exposed and badly damaged. No recruits observed
Jost Van Dyke Bakers Bay Dead Dea d <1 <5% yes Severe dam age, defoliated and dead; Many recruits
Salt Pond Dead Dea d <1 <5% no S evere damage, defoliated, with l imited resprouting; no recruits
White Bay Dead Dea d <1 <5% no Dam aged throughout, defoliated, no recruits noted
Prickly Pe ar Island Salt Pond Dead Dea d <1 <5% yes * Narrow band of short trees, all dead; few recruits observed
Tortola Sea Cow Bay Dead Dea d <1 <5% no* Badly dama ged. Scattered seedlings, very few
Paraquita Bay 1 (outer) Dead Dea d 2<5% no* Badly damaged, very few seedlings noted
Paraquita Bay 2 (outer) Dead Live 2.5 15% yes Severe damage but vegetated shrubs & recruits
Paraquita Bay 3 (outer) Live* Live 320% yes Some canopy foliage remains, moderate shrub, & recruits
Paraquita Bay 4 (inner) Live* Live 3.5 25% ye s Some canopy foliage rem ains, moderate shrub, & recruits
Paraquita Bay 5 (inner) De ad Live 2.5 20% yes Moderate damage but much rema ins, many recruits
Ber Bay De ad Dea d <1 <5% no* Badly damage d. Scattered seedlings, very few
Parham Harbor Dea d Dead <1 <5% no Scattered shrubs remain; interior may hold seedlings
Well Bay 1 De ad Dea d <1 <5% no Severe damage; very few recruits observed
Well Bay 2 De ad Dea d <1 <5% no Severe damage; very few recruits observed
Well Bay 3 De ad Dea d <1 <5% no Severe damage; very few recruits observed
Virgin Gorda Deep B ay Anc horage 1 De ad Live 2.5 10% yes Subcanopy with partial growth, numerous recruits at upland egde
Deep B ay A nchorage 2 Dead Live 315% yes S ubcanopy with partial growth, numerous recruits at upland egde
Deep B ay Ma rina 1 De ad Dead <1 <1% no* Dead and clear cut, virtually no recruits
Deep B ay Ma rina 2 De ad Dead <1 <5% ye s* Dead and clear cut, mderate a mount of recruits in dead roots
Bitter End 1 Dead Dea d <1 <1% no* Dead and some areas clear cut, virtually no recruits
Bitter End 2 Dead Dea d <1 <5% yes Narrow band of s hort trees, dead; moderate recruits observed
Biras Creek Dead Live 320% yes S ubcanopy with partial growth, numerous recruits at upland egde
G.E. Moore, Ph.D. 2018
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appeared trees were cut to maintain adjacent infrastructure such as marinas and roadways, or to allow
easier access for removing anthropogenic debris that was lodged in the mangrove (Figure 6). Overall, the
practice of clear cutting standing deadwood was relatively limited, but it is expected that it will continue
and increase as clean-up redevelopment efforts intensify.
Figure 6. Standing deadwood cut to base of mangrove prop roots in some locations in Virgin Gorda.
Summary and Preliminary Recommendations
Despite widespread damage and death of fringing mature trees, portions of sheltered, interior sites
maintained some mature trees, many of which are now flowering and will produce seed. These will be
important sites for sustainable recruitment of plant stock for restoration and conservation efforts.
Perhaps even more significantly, the majority of sites visited had a significant understory of live, rooted
seedling plants. Albeit quite young and short in stature today, these fragile recruits now have the
opportunity to burgeon forth, no longer repressed by the shady overstory. These ‘baby’ plants are the
future of BVI’s mangrove and should be carefully protected and encouraged.
In light of the fragility of this resource, I remain concerned that seedlings may be inadvertently damaged
by the practice of clear cutting of dead standing wood. Mangroves provide valuable habitat for wildlife
such as birds and invertebrates and as dead mangrove trees decompose, they release energy and return
essential nutrients and carbon to the system. The mangrove’s physical structure is mainly intact and still
buffers wave and storm energy and helps hold peat and sand in place along fragile coastlines. In turn, that
structure also protects animals and helps trap and protects mangrove seedlings that will help regenerate
the forest naturally assuming seed sources can be found. Foot traffic and dragging of cut wood by workers
threaten to trample or damage fragile seedlings and since it may be years before new plants mature and
bear seeds to populate these areas, those established seedlings are more valuable than ever now.
Fortunately, through informal communications and conversations with concerned citizens, it is clear that
the people of the BVI understand the significance of loss to this critical coastal habitat. Many hope to see
these systems restored as soon as possible in fact many have pledged direct interest in being involved,
participating, and support. Thus, with proper study, planning and support from local government and
NGO’s, significant strides can be made for conservation and restoration of this globally threatened coastal
resource in the BVI. I look forward to continuing collaboration with these and other local partners to
increase resilience and sustainability of mangroves for the future of the Territory.
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