This blog is part of the series ‘What the resilience of the Whitsundays can teach the world at the beginning of the hurricane season.’
The first thing I noticed on the islands were the grey and green background. Grey was exceptional, a colour I did not except, but so was the type of green. Coming closer I feel like I ran into a battle ground, but even closer it looks more like the birth place of new life. These are the rainforests on the Whitsundays, the forests that captured the impact of cyclone Debbie, and the same forests that are growing back, slow but steady.
Similar to mangroves and reef, forests absorb energy of cyclones and storms and slow down winds by the severe drag-friction when the cyclone passes through. In addition, rainforests might have another powerful ability to stop cyclones by its unique evapotranspiration system. Since cyclones feed themselves with moisture above the ocean, they might use the moisture of rainforests as well.
Yet, the specialised medium Forest News reports on the remarkable research of Douglas Sheil, a CIFOR senior associate and professor at the Faculty of Environmental Sciences and Natural Resource Management (MINA), Norwegian University of Life Sciences (NMBU).
Sheil explains how the unique way in which rainforests manage water precisely prevents cyclones to be shaped.
Since rainforests release moisture and aerosols in a more diffuse form, condensation is more broadly spread in space and time, hence not providing the necessary fuel for cyclones to be shaped. As a result, he believes that cyclonic storms cannot maintain themselves over, or near to, extensive forests. Which explains why cyclonic storms are near absent in the South Atlantic, where it must be formed near the rain forests of South America and Africa, with hurricane Catarina (20004) as the only exception.
Knowing this, they fear that loss of these forests would increase moisture over the ocean, while decreasing friction, hence feeding storms even more, while losing the ability to slow them down.
Unfortunately, these conclusions are in particular valid for large forests such as the Amazon, whereas narrow bands of trees are less likely to have sufficient impact.
Resilience of the rainforest
The regrowth and resilience of the Whitsundays’ rainforest is not a unique case. The story of Hurricane Maria is another great example of rainforest resilience. Maria came at land in Puerto Rico in 2017, where it turned the lush greenery into a brown mud pool. Entire areas of forest were stripped of their leaves and branches. El Yunque National Forest still does not look like it once did, yet signs of recovery can be seen.
The Bright Side of the Hurricane
Two years after Maria, the forest is slowly coming back, demonstrating the resilience of this kind of rainforest. Moreover, trees have evolved as such to cope with extreme tropical storms. For instance, the stouttrees at the mountains simply dropped their leaves and stand through the storm, preventing to become uprooted. Biologists reported how only 6 months after the hurricane, these trees already were flowering again. No leaves, but flowers.
The immediate flowering and fruiting of these trees might as well be a stress response in order to pass on their genes. Especially since sunlight is rare and precious in a dense rainforest, so when a hurricane frees up some space, creating abundance of sunlight, these trees are high-likely to spread their genetic material as fast and as far as possible. Hence, hurricanes and storms might have a bright side as well.
(the same phenomenon has been noticed by skippers sailing the Whitsundays in the aftermath of the cyclone, reported as an exceptional high rate of clarity, light and visibility through the coral reef).
Skinny but Strong
Same same but different, is the story of other parts of the rainforest where trees got their leaves back but remained skinny and developed few branches only. Yet, it demonstrates the adaptation skills of palm trees, which have by purpose no branches to survive tropical storms. Hurricane winds can pass through without resistance of branches and leaves, which is resilience to the letter.
Unfortunately, if a palm loses its few branches at the top, it dies-off. As what happened with 50% of the trees on Puerto Rico after Maria came through. Even the parts of dry forest recovered rapidly after Maria, and older and weaker branches made space for healthier parts of the trees.
Maria was not the only hurricane passing over El Yunque in Puerto Rico. As a matter of fact,
the Luquillo Experimental Forest in El Yunque is the longest continuously measured tropical forest int he world. More than 75 years of observations have measured the forest year after year, hurricane after hurricane.
Before Hurricane Maria, Hurricane Hugo (1989) already set foot on the island, with wind speeds of up to 126 mph and a maximum rainfall of 17 inches. Yet, not even five years after, vegetation was already growing until levels similar to before the storm. While 10 years after stemdensity was even higher than before Hugo.
Moreover, the World Resource Institution appoints to the fact that a hurricane not only cause losses, but creates a new fertile layer of soil, where dead trees and forest is converted into the beginning of new forest life.
No wonder, Puerto Rico had understood the relevance of forests, which resulted in increased forestation cover from 6% in 1940s – with high clearance due to agriculture – to about 50% in 2010.
Rainforest under treat
Yet, globally only 6% of the Earth’s surface is still covered with rainforest, while about 17% of the Amazon has been destroyed only in the past 50 years, and the current burning situation will increase this percentage dramatically.
Moreover, according to National Geographic, two countries only accounted for 46% of the primary tropical rainforest loss in 2018: Brazil and Indonesia (the latter for palm oil production). In addition, in various other countries, from Colombia to Democratic Republic of the Congo, loss rates are rising remarkably.
Yet, once rainforest is lost, it is nearly impossible to restore, let alone the biodiversity within it that has been lost.