Hurricane recovery programme: British Virgin Islands 2018 Part 2:
By Kevin Martin
2018-10-09
As the Arboricultural Manager at RBG, Kew, I get opportunity to engage with our various global partners. One of these was to lead a team to the British Virgin Islands. The Islands suffered extensive damage during a hurricane earlier in the year, and I was invited to visit to help with the recovery operation. As I explained in part 1, we faced some unusual challenges, including the need to take all of the kit with us, on the plane, with access to a rather small budget. In part 2, I share about our discoveries.
This was a very exciting opportunity to use our Arboricultural skills to help people in need. We had the great pleasure of having tea at the Governors house. This was really lovely for us all to meet the Governor of the British Virgin Island, His Excellency Augustus Jaspert and his wife Mille Jaspert. We were to discuss how this recovery was going to take shape. It was very interesting to hear the immediate action needed after the storm had struck the island, with inmates from the prison on the island escaping and the UK navy helping to recapture such escapees. It was alarming to hear how the UK Navy support has only seen this from of damage in war zones like Iraq and Afghanistan.
So, after this interesting discussion, it was decided that we would firstly tackle the Botanic Gardens to allows us to make this area safe and enable the gardens to reopen to the visiting public as the income from tourists is necessary for the economy of the island.
The first step was to carry out a negative survey of the site to establish a priority of work. This first survey was to identify what trees needed removing. By doing this, it allowed the team to start work the next morning allowing me a couple of days to carry out a full assessment of the area and put in place the plan of mitigation for the damaged trees.
Whilst the team got on with the removals, I sent about mapping, zoning, and carrying visual tree assessment with management plans to enable the restoration pruning of the remaining trees from the storm. Working with the tropical trees was a particularly fascinating task, as was observing the speed of growth which they can produce. For a high percentage of the trees, we carried out crown reductions to remove the storm damaged branches.
This form of tree work has not been carried out in the British Virgin Islands before, with most trees in the urban environment having never being pruned at all, and many of them being large Mahogany trees lining the streets of Road Town. As I discussed with the national parks trust who manage the garden, this is the first step. Further pruning to the retained trees will be needed over the next 2 years to allow for the regrowth from this pruning to be managed. This is the difficulty encountered when visiting different countries with complete change in culture towards trees and urbane canopy cover.
I am pleased to report that we managed to remove all the trees that posed a risk and also managed to finish all the restoration pruning which was a fabulous result. Our original plan was to only to open half of the botanic garden; we never expected to open the whole garden. This was down to a very big team effort. With the heat and humidity, we started work at 5am and finished by 1pm allowing us to rest in the afternoons when the temperature peaked around 33 degrees and humidity reached 90%. We needed the afternoon to rest and stay as cool as we could. This high heat made it very uncomfortable to work in.
Managing to open the Botanic Gardens in the first week allowed us to move on the Governors House. The damage received at this site was less than the Botanic gardens. However, the number of trees needing restoration pruning was much higher. This included some very dead Norfolk Pines and large Mahogany needing restoration pruning. Again, I am pleased to say we managed to complete all the work needed to make the site safe to reopen. We never envisaged we would be able to complete all this work in the conditions we faced.
I spent a couple of days away from the team as they carried on doing the hard work of making the governors house safe. This was to spend time with members of the park trust looking at the urban forest and Sage Mountain which is a nature reserve.
Sage Mountain
Sage mountain has been devastated by hurricane Irma. With severe depletion to the canopy cover, this canopy loss is mainly caused by the loss of the plantation of West Indian and Honduran mahogany trees (Swietenia mahogoni and Swietania macrophylla). This loss of canopy is going to have a multitude of impacts to the local environment, ecosystem and biodiversity.
The most significant effect will be the loss of habitat which can lead to the loss species. As with any ecosystem some individual species may be intolerant to loss of a particular tree. The loss of species can have a wider affect to the surrounding ecosystems, as food chains often cross ecosystem boundaries (Johnson, 2017)
With the large amount of canopy loss, it will cause evapotranspiration which is the loss of water from the forest back to the atmosphere. This canopy loss disrupts this cycle causing in extreme circumstances less rain fall plus causing drier conditions over broad surrounding areas, this can lead to drought conditions. (Johnson, 2017). This loss of moisture can lead to a deficit in recharging water tables which in return can affect water flow into rivers and other water ways. This loss of canopy cover can lead to an increase in the risk of flooding and erosion of sediment into rivers (Johnson, 2017).
With Sage Mountain being of dense canopy prior to Hurricane Irma, this loss of canopy will affect light levels to the understorey of the forest. Exposing the organic layer to sunlight, this will cause the loss of nutrients and moisture. With the raining season this will cause dry soil to be washed away due to the lack of root structure and water take up from established trees (Johnson, 2017). If soil loss is drastic this will impact the re-establishment of the forest.
With regard to the safety of the trails, this is of upmost importance with the trails being a tourist “must see” plus with local people and schools using these trails for leisure. With the effect of hurricane Irma very much still present with mature trees with root heave, full trees still hung up within neighbouring trees over the trail and with large broken branches, with hung up trees in canopy of neighbouring trees, all still very close and/or over the trails. Work has been carried out to make safe these trails. However, from the recent visit there is still a high risks trees over the trails which would need mitigation to make the trails safe.
With regard to the urban forest, the main issues from observation in the urbane landscape, is the number of dead trees which are now high risk. These dead trees are going to become unstable and prone to failure in a very short period of time. These trees are to be removed as soon as reasonably practicable. With the large amount of urban tree loss, the situation is going to have ramifications for many years. One being the loss of shade trees which is paramount given the local climate. Urban trees are highly effective at ameliorating urbane warmth at ground to building height. Tree shade reduces stored heat within urbane surfaces (concrete).
Research has showed that shade trees have reduced surface temperature reduction from 11-25oc for walls and roofs (Akbari et al, 1997). In parked cars a reduction of 25oc (Scott et al, 1999). Urbane heat islands are used to describe the above characteristics, which is the warming of atmosphere and surfaces in the built environment. (Voogt, 2002). Heat islands develop when a large percentage of natural land cover in an area is replaced with built surfaces which trap incoming solar radiation during the day, re-radiating at night (Quattrochi et al, 2000). With large urban trees providing important filters to pollutants and fine particulates, also trees planted in the correct position can reduce air conditions needs by 30%. (Anon., 2018)
All of the observations made from our trip were compiled into a report and published in September. This has now been submitted to National Parks Trust of the British Virgin Islands and the Governor office. This report has been received very well, with the Governor trying to get the replanting of the urbane canopy put forward as part of the recovery program.
This link is a video of the team’s effort recorded and edited by the team. Please do take a look: https://youtu.be/2JJo7p9Kf_A