The Benefits of Cyclones

It's been over a year since the World Water Forum in Korea, where one of the members of the typhoon committee argued the necessity of studying the benefits of cyclones, which I since then did. Preceding a presentation at the 7th International Conference on Water Resources and Environment Research  in Kyoto, June 5-9, I here provide an overview of the literary findings of benefits of cyclones.

Cyclones often cause heavy damages and destruction to infrastructure and human lives, but the potential benefits of cyclones remain understudied. Several of these benefits could serve as an integral part of ecosystem based disaster risk reduction plans, when viewed as ecosystem services. For this purpose, we examined how the benefits of cyclones could be valued as ecosystem services. In phase one of this study, we scrutinized existing studies regarding potential benefits of cyclones.

The image shows a compilation of the 14 benefits of cyclones as described in the gathered studies on the topic, which we organized by approximate location (troposphere, biosphere, epipelagic zone) and order (cause and effect) of occurrence. More details follow after the break below.

The found benefits contained the following examples:

1) Shielding against solar radiation ►Reduced global warming

The energy impacts of one cyclone included a reduction of the radiation energy in the atmosphere by 0.5 x 1020 joules, equivalent to 10% of the annual global energy consumption.

2) High wind speeds ► Wind Power

About 30% of the cyclones in China can damage wind farms. However, in case the wind speeds remains  less than 88 km/h, ± 55% of cyclones lead to an increase in harnessed energy, even doubling the average amount of energy harnessed. 

3) Drop in air temperature ►Reduced effects of heat waves and power consumption

Cyclones have a net cooling effect of around 0.17-0.25◦C per day or 2-6◦C during several days, which is an exceedingly crucial relief from increasing summer temperatures and heat waves. Cyclones help move warm air from the tropics to the poles, and on average release an amount of heat energy equivalent to 50-200 EJ (exajoules, quintillion joules (10^18)) daily. 

4) Spreading and cycling of materials (aerial/land based) ►Increased pollination and spreading of nutrients, alleviation of toxic salinity, spreading of fauna

Cyclone clouds extend up to the tropopause (the boundary between the stratosphere and the troposphere, which is about 9km high at the poles and 17 at the equator). Along with the size and traveling distance of a cyclone being several hundreds of kilometers, and the high wind speeds, cyclones are responsible for the aerial distribution of biologic material, possibly as much as oceanic. These materials would otherwise remain stationary or confined to a local area. This aids genetic spreading and pollination, and in turn stimulates biologic diversity and evolution.

5) High amounts of precipitation ► Water use/storage

Cyclones are the source of >50% of the annual precipitation in Japan; 30-50% in Western Australia; ±30% in Hong Kong; >25% in India, the Philippines, Vietnam, Thailand, Indonesia; and ±15% in the Gulf of Mexico.

6) Contributing to dynamic changes (terrestrial, marine, fluvial) ► Creation/maintenance of barrier islands and atolls serving as flood protection and increasing biodiversity; flushing of rivers reducing toxins and increasing fish spawning grounds

(Uninhabited) barrier islands are easily eroded and supplemented by wind, tides and currents; a dynamic process which is amplified by cyclones. These small islands could diminish due to rising sea levels, and cyclones could hypothetically provide sufficient dynamics to replenish their size. Cyclones support wetland flood dynamics and sediment flushing in rivers. Rivers can receive the higher amount of discharge required for the periodic flushing of sediments only from cyclones. This flushing can move fine sediments and toxic materials, and opens the riverbed for aeration and fish spawning locations, which are part of the natural dynamic equilibrium of river systems.

7) Open forest patches leading to favorable circumstances for species ►Increased forest biodiversity, production, number of breeding grounds and habitats

Cyclones increase net production by continuous rejuvenation of forest to early successional states by cyclones. Disturbances enable the release of nutrients stored in biomass, litter and sediments, which lead to higher net productivity and biodiversity.  

8) Pollutant transportation ►Reduced air pollution, reduced ground water pollution

Precipitation aids the transport of pollutant particles from the air as acid rain into the groundwater system or through the air. After one cyclone affected Yucatán, Mexico, in 2005, the increased water levels in wells decreased salinity levels as well as diluted pollutants in all wells of the study area but one. 

9) Carbon sequestration ► Reduced global warming

A study in Taiwan in 2004 found a river conveyed about 500,000 tons of carbon particles during a cyclone, which was the rough equivalent of 95% of the regular annual average of carbon particle transport.

10) Extermination of pests and their habitats ► Reduced spread of disease through pests or harmful algal blooms

In 1965 a hurricane wiped out a population of mosquitoes and its breeding grounds by depositing sand on an island off the coast of Alabama, USA.

11) Redistribution of forest resources ►Timber for livelihoods

After one cyclone occurred,  218 tonnes of dead material were deposited in a Mississippi marsh, whereas no attached materials were transported. 

12) Oceanic turbulence leading to heat flux ►Alleviation of coral bleaching

Cyclones help move heat from the tropics to the poles and drive the thermohaline circulation by inducing upper-ocean mixing. During a cyclone the sea surface temperature cools about 1-3˚C. 

In one study the thermocline and halocline depths deepened by about 10m. A lowered ocean temperature is especially beneficial to coral reefs, which are highly sensitive to heat stress and may undergo coral bleaching after prolonged exposure. Cyclones benefit bleached coral recovery as wind-forced vertical mixing can lower sea temperatures by as much as 5°C. This reduces thermal stress on corals, which in turn reduces the time required to recover from bleaching. The cooling effect of cyclones significantly reduced both the extent and recovery time of coral bleaching in the Caribbean in 2005.

13) Oceanic turbulence leading to marine life migration ►Increased fishing opportunities

Changes in thermocline and halocline depth lead marine organisms to migrate to areas with optimum temperature and food sources. Changes in the halocline depth affect zooplankton, which tend to remain and accumulate in water with higher salinity where they require less energy for movement. Patterns of prey and predator relationships change as marine organisms migrate vertically. The sea surface salinity increased by 0.3 pss (practical salinity scale) after a cyclone passed. 

14) Oceanic turbulence leading to marine life production ► Increased phytoplankton

Oceanic turbulence contributes to primary production, which occurs in the upper 50 to 150m (euphotic zone) which allows for photosynthesis. Cyclone winds increase vertical mixing of the upper layers of the ocean, which transports nutrients from lower to higher layers, increasing photosynthesis and thereby the production of phytoplankton. A 3-day cyclone caused 30x increase of the surface chlorophyll-a concentration, equivalent to about 3% of the South China Sea’s annual production. Given the average duration, frequency and intention of cyclones, the contribution of cyclones to production in the South China Sea was estimated at 20-30%.