Losing Home #3: Storms

This article is part of a series exploring the ramifications of climate change on the physical habitat of coral reefs and the consequences for the various dependent communities

By Evan Quinter

Edited by Sara Gagliardi

As a series, Losing Home attempts to compile the various consequences of losing coral reefs as a physical habitat. We’ve discussed how warmer waters stress stony reef-building corals and the resulting migration of dependent marine species. The pressures of climate change are causing a radical change of the collective reef ecosystem. But there’s another factor brewing on the horizon, one whose destructive capabilities will only intensify due to climate change – storms.

Over the past 25 years, NOAA observed 17 above-average Atlantic hurricane seasons. By studying the relationship between sea-surface temperature and precipitation, climate scientists are able to correlate increases in extreme weather events to climate-induced temperature rises. 

The association between extreme weather and climate change is difficult to discern, as the ability to model extreme weather events requires accounting for an exceedingly complex system. Thus further research is needed for definitive correlations to link extreme storm events to greenhouse gasses. Due to climate change or not, researchers predict a 60% increase in extreme storms by 2100.

Directly in the path of these equatorial storms are coral reefs. Among their many natural benefits, coral reefs serve as a buffer zone between oceanic storms and land, reducing wave action and erosion along the coast. Their mitigation of flood damage saves countries roughly $4.3 billion annually, particularly for island and coastal nations. Since reefs are degraded by other climate factors, like bleaching and heat stress, then their capacity to buffer storms is impeded, leading to weathered reefs, eroded coastlines, and battered communities.

The destruction of extreme cyclones is already evident along the Great Barrier Reef (GBR). Researchers studied the aftermath of three unusually strong cyclones over 5 years, noting extensive coral cover loss throughout the GBR and up to 68% loss in the central-southern region. Subsequently, species richness and abundance in the GBR decreased. The predictions worsen as researchers predict major storms (spread over 300 km) will cause coral loss for reefs over 800 km away from the eye of the storm. 

Figure 1: The distance it takes for tropical cyclones of various sizes to fall from hurricane force winds (33 m/s) to gale winds (17 m/s). For big storms, coral reefs could be impacted by cyclones over 800 km away from the eye of the storm. Modified from Puotinen, M. et al., 2020

But beyond this cyclonic damage, climate-induced storms caused unexpected changes in reef systems. Between August 2015 and April 2017, researchers at Kenting National Park (KNP) studied environmental parameters during 7 major typhoons. The storms produced the expected physical damage to branching coral, along with high nutrient levels to support macro-algae dominance. At the same time, the greater rainfall lowered sea-surface temperatures around KNP, which reduced thermal stress and potentially mitigated bleaching from the 2016 El Niño. Although local conditions determined the level of thermal relief, the storms at KNP simultaneously harmed and protected coral reefs.  

To complicate this relationship further, major storms do not always have a significant effect on the reef. After observing the soundscape (a measure of reef health discussed previously) of a Florida Key reef during Hurricane Irma, researchers observed only minor shifts in acoustic activity. The daily acoustic patterns of the coral reef, “…were relatively resilient to acoustic energy exposure during the storm.”

Figure 2: The low frequency sound production patterns in Eastern Sambo, a no-entry reserve in the Florida Keys, before and after Hurricane Irma. The right-side panels depict average sound pressure levels during the same 5 days and nights. Although mid-frequency production may have been weakened after Irma, the high and lower frequencies seem to be relatively unaffected. Modified by Simmons, K.R. et al., 2021

Unlike the direct relationship between thermal stress and coral health, the measurable impact of extreme storms on coral reefs is complex. The characteristics of each major storm, combined with the conditions of local environments, makes modeling future storm events difficult. More research must be conducted to fully understand the relationship between climate-induced storms and coral reef health. However when paired with other stressors caused by greenhouse gas emissions, the ramifications of extreme weather creates major destruction on reef habitats and coastal communities. The same solution appears for each risk to the reef habitat. To save coral reefs, we need to reduce greenhouse gas emissions. Otherwise, we can expect even greater storms.

Cover Photo Credit to Dexmac on Pixabay

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