Marine heatwave threatening life below water
| Policy Research and Advocacy Team, Friends of the Earth (HK)
With last month being the hottest October on record, 2023 is on
track to be the warmest year in history.As the Earth's climate continues to warm, we are witnessing a range of
consequences that are affecting both the environment and human livelihoods.
Coastal communities are increasingly being exposed to climate
change-driven extreme weather events and rising temperatures. Around 3.6
million people live in areas that are vulnerable to these climate impacts.The arrival of El Nino further amplifies these effects, leading to extreme
heatwaves breaking temperature records worldwide.Heatwaves are not confined to land; the ocean is also exposed to these extreme
The average ocean surface temperature broke record levels in August,
reaching almost 21°C.In some areas, such as the Florida Keys, water temperatures even exceeded 38°C
at one point–as hot as a hot tub.Marine heatwaves, which have become more intense and longer-lasting under
climate change, have doubled in frequency between 1982 and 2016.
In addition of warming waters, Florida
Keys is also threatened by rising sea levels (Image source: Florida Keys News
The consequences of a warming ocean are wide-ranging. The ocean
plays a vital role as the Earth's largest carbon sink, absorbing carbon dioxide
from the atmosphere.However, as the ocean heats up, it becomes less efficient at capturing carbon
dioxide, exacerbating global warming further.
The ocean carbon cycle (Image source:
Warming waters also contribute to the intensification of storms by
providing more energy and moisture.This leads to stronger and faster typhoons, posing risks to coastal communities
and maritime activities.
Ecosystems like coral reefs and kelp forests, which are crucial for
marine biodiversity and provide numerous benefits to humans, are under
increasing thermal stress. Coral reefs, for example, undergo bleaching when
exposed to prolonged periods of high water temperatures. Kelp forests are also
declining at a rate of about 2% per year,disrupting the delicate balance of marine ecosystems.
Marine heatwaves are causing Australia’s
Great Barrier Reef to undergo bleaching (Image source: Getty Images)
The warming ocean also directly affects the fishing industry. As
water temperatures exceed comfortable ranges, certain fish species move
poleward in search of cooler waters.This forces fishermen to travel further out to catch fish, leading to increased
fuel consumption and carbon emissions. Additionally, both wild and farmed
species such as crabs and oysters experience stunted growth or mass die-offs
due to changing ocean conditions.This results in significant economic losses and sometimes necessitates setting
moratoriums to stabilise populations.
In response to these challenges, communities are taking measures to
build climate resilience in the fishing industry. For instance, Japan's
Fisheries Agency is promoting the use of electric fishing boats to reduce fuel
costs.In Australia, the Commonwealth Scientific and Industrial Research Organisation
is collaborating with a salmon hatchery to develop heat-tolerant strains of
salmon.In Europe, proposals are being made to encourage the sales and consumption of
alternative, more sustainable species to reduce vulnerability to climate
Increasing diversity of the fishes we eat
can improve the sustainability of the fishing industry (Image source: Darryl
It is crucial to recognise that climate change is not all just about
hotter summers and more intense typhoons, it affects food security as well. Global
warming has a profound impact on the ocean and the fishing industry, adversely
affecting fish populations, coral reefs, and other important habitats. More
than 3 billion people rely on fish and shellfish as important sources of
nutrition,and 600 million people depend on fisheries and aquaculture for their
livelihoods.Even in Hong Kong, seafood is a significant part of our diet, and the local
fishing industry meets nearly one-fifth of the demand.It is imperative that we address climate change and build climate resilience
for the long-term sustainability of the ocean and the livelihoods of those who
depend on it.