Climate Change Impacts Japan's Marine Life: Kelp Endangered in Hokkaido Waters

Climate Change Impacts Japan's Marine Life: Kelp Endangered in Hokkaido Waters

In the waters surrounding Japan, a silent crisis is unfolding. Over the past century, ocean temperatures have increased by 1.33°C, a level twice the world average [1]. This temperature rise, driven by global warming, poses a significant threat to multiple kelp species in Japanese seas.

According to a study by Hokkaido University, four varieties of kelp—Saccharina longissima, Arthrothamnus bifidus, Saccharina gyrata, and Saccharina coriacea—could disappear completely from Japanese seas due to global warming by the end of the century [2]. Under a worst-case scenario, up to six kelp varieties could vanish from Japanese coastal waters [1].

The sensitivity of kelp species to thermal stress is the primary cause of concern. As ocean temperatures rise, these underwater forests face increased stress, affecting their distribution, survival, and overall health. This decline in kelp populations has broader ecosystem implications, disrupting marine food webs and the productivity of related marine species [1].

For instance, warming reduces cold-water habitats like Hokkaidō’s drift ice, which supports essential nutrients and phytoplankton that sustain species such as scallops [1]. The loss of these habitats is a complex, cascading effect of ocean warming on the marine ecosystem as a whole.

In addition to the simulated impacts, more frequent and intense marine heatwaves are becoming a reality. These periods of anomalously high water temperatures are causing mass kelp declines and ecosystem collapses worldwide [4][5]. These heatwaves contribute to the loss of kelp forests, which are vital habitats, affecting species from plankton to whales and causing widespread mortality events in marine life due to heat stress and linked diseases.

The town of Rausu, located on the Shiretoko Peninsula in eastern Hokkaido, is known for producing high-grade konbu (kelp), a key ingredient in Japanese cooking. However, in autumn 2023, the ocean surface temperature off the coast of Rausu reached 25°C, an unprecedented temperature for the region [7]. This rise in ocean temperatures has resulted in more frequent marine heatwaves in Japan, threatening the future of konbu production.

In 2024, 8,213 tons of konbu were harvested in Hokkaido, a decrease from previous years and falling below the 10,000 ton mark [8]. In 2023, cultivated konbu was most heavily impacted, with many producers suffering a 50 to 80% decrease in harvest [9].

The decline in konbu harvest is not the only concern. Hauls of scabbard fish, a large fish prized on Japanese tables, are declining in western Japan, while they have increased 25-fold over the past decade in the northern prefectures of Iwate, Miyagi, and Fukushima [6].

The loss of kelp and the decline in marine species have significant ecological and economic repercussions. Measures being undertaken to reduce global warming, such as energy-saving initiatives and the introduction and expansion of renewable energy, are essential for protecting the future of seafood that is so dear to Japanese people.

Moreover, the impact of global warming is not confined to the surface. It is having an impact below the ocean surface, unseen by most people [3]. The area of ice floe in the Sea of Okhotsk south of the 46th parallel, close to Hokkaido, is forecast to fall to one-third of the average area from 1994-2017 by 2050 based on the lowest level scenario of greenhouse gas emissions [10]. Some forecasts suggest that in the future there may even be years when no drift ice appears off Hokkaido's coast.

In the face of these threats, it is crucial to act now to protect the marine ecosystems of Japan and preserve the valuable seafood they provide. The future of Japanese cuisine and the health of the marine ecosystem depend on it.

References: 1. Climate Change and Ocean Warming Threaten Japanese Kelp Species 2. Study: Four Kelp Varieties Could Disappear from Japanese Seas by End of Century 3. Global Warming: Its Impact Below the Ocean Surface 4. Marine Heatwaves and Mass Mortalities: A Global Overview 5. Marine Heatwaves: A Global Synthesis and Perspectives 6. Scabbard Fish: Declining in Western Japan, Increasing in the North 7. Autumn 2023: Unprecedented Ocean Temperature off Rausu Coast 8. Konbu Harvest in Hokkaido Falls Below 10,000 Tons in 2024 9. Cultivated Konbu Heavily Impacted in 2023 10. Sea of Okhotsk Ice Floe Area Forecast to Fall to One-Third by 2050

1. The global warming crisis, apparent in increased ocean temperatures, poses a lethal threat to specific kelp species around Japan.
2. The study by Hokkaido University indicates four kelp varieties, such as Saccharina longissima, could disappear completely from Japanese seas due to global warming.
3. In a worst-case scenario, up to six kelp varieties may vanish from Japanese coastal waters.
4. Thermal stress is the primary factor affecting the survival and health of kelp species in response to global warming.
5. With ocean temperatures rising, kelp forests face increasing stress, disrupting their distribution and overall health.
6. Disrupted marine food webs and productivity of related species are wider consequences of the decline in kelp populations.
7. Warmer oceans lead to the loss of essential habitats like Hokkaidō’s drift ice, threatening species like scallops.
8. Marine heatwaves, causing mass kelp declines and ecosystem collapses globally, are becoming more frequent.
9. These heatwaves are contributing to the loss of kelp forests, vital habitats, affecting species from plankton to whales.
10. In Rausu, known for producing high-grade konbu, an unprecedented ocean temperature of 25°C in 2023 affected the future of konbu production.
11. The decrease in konbu harvest in Hokkaido in 2024, falling below the 10,000 ton mark, is a concern for the local economy.
12. Harvest decline affected cultivated konbu significantly, with many producers suffering a 50 to 80% decrease in harvest in 2023.
13. Declining scabbard fish hauls in western Japan and their increases in northern prefectures pose further implications for Japanese cuisine and marine ecosystems.
14. Reducing global warming through energy-saving initiatives and renewable energy expansion is vital for the future of seafood essential to Japanese people.
15. Global warming impacts stretch beyond the surface, affecting marine ecosystems unseen by many.
16. The area of ice floe in the Sea of Okhotsk is forecast to fall to one-third of the average area from 1994-2017 by 2050.
17. Forecasts suggest there may be years when no drift ice appears off Hokkaido's coast in the future.
18. Given the threats to marine ecosystems, it is crucial to act now and implement measures to protect them.
19. The future of Japanese cuisine, which relies on diverse marine species, depends on preserving the ecosystems they inhabit.
20. The global warming crisis extends beyond science and land-based industries, affecting even food-and-drink businesses, such as seafood production and cooking.
21. Personal-finance needs to align with concerns about the global climate-change crisis and invest in solutions, such as energy-efficient businesses and environmental-science companies.
22. The advent of electric-vehicles, real-estate projects equipped with data-and-cloud-computing technology, and online-education platforms in the education-and-self-development sector contribute to reducing the global-warming crisis.
23. Social-media platforms can help raise global awareness about the climate-change crisis, while casino-and-gambling websites offer opportunities for personal-finance investment in climate-change solutions.

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