27 July 2018
No leaves left behind on the island: Hurricane Irma destroys forests
In September 2017, Hurricane Irma broke records when winds devastated the Caribbean. In Kew’s first known response to a humanitarian crisis, the Tree Gang and our science programmes joined forces to help restore the island habitats.
'It was devastating.'
Colin Clubbe, Head of Conservation Science, sums up his observation of the impact of Category 5 Hurricane Irma on the British Virgin Islands (BVI).
‘People I’ve worked with for years had their houses blown off the side of a mountain. Roads were impassable.
‘The whole island was basically brown, defoliated. The hurricane stripped it. There were no leaves left’.
The 180mph winds not only destroyed buildings but also the lush plant life that the islands’ main industry- tourism- relies on.
‘These trees were dangerous after storm damage. There were no resources to help. The nearest arborists were in Puerto Rico, which had also been hit by Hurricane Maria.
‘My team assessed the situation and we found we needed to get the J.R. O’Neal botanical garden- which was totally blitzed - back on its feet for the public and visitors.’
Colin’s science team would combine work with Kew’s horticultural team who are experts at tree management to implement the plans.
The tree gang
Kew’s Tree Gang – or arboricultural unit- are a sturdy six-man team who look after the Garden’s 14,000 wonderful trees.
This would be the first time they use their skills to alleviate the impact of such a disaster.
Kevin Martin, manager of the unit, explains that this assignment was tricky from the get go.
‘First of all, we had to see how long we were able to be released for. Two weeks was about the most we could manage.’
‘Then we had to scale down everything we normally use because of baggage allowances. That took a lot of judgement and experience as we’d only seen photos.
‘We took two climbing kits, a complete rigging kit and three chainsaws including a 20” ground saw to cut bigger stems.
‘When we arrived, we did exactly what we do at Kew after a major storm; a negative survey. I marked any tree that was dangerous for felling and the team started straight away. Then I did risk assessments and future management plans for the remainder of tree collection.
‘After that, we did what we could to restoration prune the rest. We had a great bunch of guys from the National Parks Trust to help with the clearing of the debris.
'I learned on the first day that we couldn’t work the afternoons because of the heat and humidity.
'We readjusted our working hours, getting up at 5am and working through to 1pm to manage the heat.'
The gardens had lost nearly half of its collection. The Tree Gang pruned 20 trees and removed a further 22 and met with city leaders to advise on urban forestry maintenance.
Colin says that the full impacts of Hurricane Irma might not be seen for a while.
‘The Caribbean is one of the world’s most important biodiversity hotspots. The Caribbean flora has about 13,000 plant species with about half of these are endemic to the region. Small islands are a microcosm of evolutionary and ecological processes where there are lots of interesting endemic plants.
‘We’ve documented 648 native species of plants in BVI and maybe 15% of those are trees.
‘That’s why we had already identified it as a Tropically Important Plant Area, where Kew has been working for nearly 20 years, conserving seeds and helping their Government to institute conservation programmes.’
The team now needs to return to resurvey the damage and see what interventions are needed, and whether some of the seeds stored in the Millennium Seed Bank need to be repatriated.
Colin says, ‘This is exactly the kind of thing that Kew should be involved in globally. Safety and re-establishing green spaces for people to feel comfortable, when every morning they walk outside to see piles of rusting cars and are still reminded of the worst recorded storm.’
The future impact
Kevin estimates that the popular Sage Mountain lost nearly the whole of its north-facing canopy cover. He continues ‘I would say on a wider scale, the British Virgin Islands lost 75% of its canopy cover in urban landscape.
‘That’s going to be extremely important. Some of those are shade trees. The ground is concrete which radiates heat through the night.
‘The trees kept everything cool by releasing water through their leaves, and the shade helped people stay cool. They’ve lost that.
‘There are still dangerous trees alongside main roads; we drove by two schools with large dead mahogany over play equipment.’
Colin continues, ‘It is possible that we have totally lost some habitats.
‘As humans, we have changed things in such a way that some of the natural resilience had been lost.
If, for example, the land is cleared to make way for a new road, the trees that hold the soil together are sometimes lost. Also, the removed trees are often those that have become adapted to hurricanes. The trees without this adaptation become more exposed and susceptible to wind damage.'
‘The ecosystem got used to the canopy cover from the mahogany. The soil is going to change now; already moisture levels have changed because they are now baked by the sun. Soil erosion will happen quickly as the roots die.
‘In my opinion, because it has been so devastating the whole biodiversity is going to change.'
It’s not all doom and gloom.
Colin remarks, ‘What’s interesting is that these ecosystems have evolved in a hurricane belt. Intact habitats are naturally resilient. When a hurricane knocks down a plant, it can root again.
‘The winds took out the canopy cover, so you now have more open light and lots of rain. It greened within the short time we were there. The mangroves are recovering. They are the great protector.
'In one sense, nature can look after itself.’