tides

Mangrove forests and rising seas

December 6, 2024 By EarthWise Leave a Comment

Mangrove forests play a vital role in the health of our planet. They protect coastal regions by acting as natural barriers against storms, erosion, and flooding. The intricate root systems of mangrove forests, which allow the trees to handle the daily rise and fall of tides, also serve as biodiversity hotspots, attracting fish and other species seeking food and shelter from predators.

But mangrove forests around the world are under increasing threat from deforestation, coastal development, and climate change. In fact, according to a new study led by researchers from Northumbria University in England, the mangrove trees in the Maldives are actually drowning.

The research, which was recently published in the journal Scientific Reports, found that sea levels around the Maldives rose more than 1.18 inches per year from 2017 to 2020. An unusually intense climate phenomenon, known as the Indian Ocean Dipole, occurred toward the end of this period, causing warmer sea surface temperatures and an increase in sea level in the Western Indian Ocean.

While mangrove forests can naturally keep pace with gradually rising seas, this rate of sea level rise was too fast. The rising sea level meant that seawater effectively flooded mangrove forests, causing many trees to lose their resilience and die. Some islands in the Maldives have lost more than half of their mangrove cover since 2020.

Since mangrove forests also store massive amounts of carbon, the research team fears that the loss of mangrove forests could release large amounts of carbon, further accelerating climate change.

The researchers warn that the findings in the Maldives could have implications for coastal ecosystems around the world.

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“Drowning” mangrove forests in Maldives signal global coastal threat

Photo, posted February 11, 2015, courtesy of Alessandro Caproni via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Protecting coastal areas with tidal range electricity generation

February 13, 2024 By EarthWise Leave a Comment

Tidal range electricity generation uses the water level difference between high and low tides to operate generator turbines. The method requires the construction of barrages and sluices to capture water during high tides and then release it during generation at low tide. Tidal range generation is predictable renewable energy driven by the gravitational pull of the moon and sun.

It is only a practical scheme in those places that have large tidal ranges. The largest tidal range in the world is in the Bay of Fundy in Canada. The second largest is the Severn Estuary, in the UK. Tidal ranges are large in many places around Britain’s coasts. But they are also vulnerable to flooding and surges from rising seas.

A new study by Lancaster University in the UK has found that the environmental and economic benefits are huge because tidal range barrages can protect coastal areas from flooding and sea level rise. With two-way generation and pumping, the full range of existing tides can be maintained to protect and support low-lying intertidal areas such as saltmarshes and mudflats. High tides can be limited to existing levels simply by closing sluices and running turbines and low tide levels can be maintained by pumping. The study determined that with modern technology and operating procedures, these so-called estuarine barrages may be the only practical way to protect vital coastal habitats.

Earlier work by the researchers found that tidal range projects under commercial consideration in the UK can produce about 5% of the country’s electricity use and additional projects are feasible for 4 or 5 times as much generation.

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How tidal range electricity generation can protect coastal areas from flooding

Photo, posted August 17, 2014, courtesy of Andrea via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The Most Powerful Tidal Turbine Is Generating Power | Earth Wise

October 1, 2021 By EarthWise Leave a Comment

The movement of waves, tides, and currents in the ocean carry enormous amounts of energy that in principle could be harnessed and converted into electricity to help power our homes, buildings, and cities. Oceans cover nearly three-quarters of our planet, and the most populated areas of the world are located near oceans.

Ocean energy technologies lag far behind solar and wind power and remain mostly undeveloped. This is a result of the unique challenges standing in the way of widespread deployment. There are the considerable expenses of early-stage development, the wide variety of technical approaches from which winning strategies have yet to emerge, and the substantial challenges of operating in the ocean environment that include the physical impact of waves and tides, powerful and unpredictable weather, and corrosion and bio-fouling from the ocean and its inhabitants.

Despite these challenges, there is ongoing progress on ocean energy. The world’s most powerful tidal turbine has come online this past April. Known as the Orbital O2, the floating turbine is anchored in Scotland’s Fall of Warness, where a subsea cable connects it to the European Marine Energy Center.

The turbine produces enough electricity to meet the demand of about 2,000 homes in the UK. It is expected to operate for the next 15 years.

Built by the Scottish engineering company Orbital Marine, the O2 was financed by the ethical investment platform Abundance Investment as well as being supported by the Scottish government and the European Union. Orbital Marine’s goal is to commercialize this technology to play a role in tackling climate change using this new green energy technology.

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The world’s most powerful tidal turbine is now generating power

Photo, posted June 12, 2015, courtesy of David Stanley via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The World’s Largest Tidal Device | Earth Wise

June 18, 2021 By EarthWise Leave a Comment

Most of the world’s activity in renewable energy is focused on solar and wind power. The use of both is expanding rapidly. But there is also marine energy to be exploited. Ocean waves and tidal movements hold huge amounts of energy. Estimates are that the European Union could get 15% of its power from marine sources. But ocean energy is currently expensive and there are significant technical challenges still to be overcome.

The world’s largest tidal power device will soon begin testing off the coast of Scotland. The 680-ton, 240-foot-long, airplane-shaped device will be connected to the European Marine Energy Center for testing.

The device, built by the Scottish company Orbital Marine Power, is designed to produce 2 megawatts of electricity, enough to power 2,000 homes. It has a pair of 52-foot-long turbines attached to two wings.

Compared to wind and solar power, the marine energy sector has been much slower to develop because of the many difficulties of working in harsh marine environments as well as the technical challenges associated with harnessing power from waves and tides. But ocean waves and tidal movements hold enormous amounts of energy and have the advantage that they are available at all times, unlike wind and solar energy, which are variable in nature.

Experts say that the future of tidal energy lies with arrays of floating or sea-bottom-mounted turbines that capture the energy of tidal currents in unobstructed waters. There are various places around the world where this is an attractive opportunity, most notably in Nova Scotia’s Bay of Fundy, where the world’s most extreme tides – rising and falling more than 50 feet – contain vast amounts of power.

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The World’s Largest Tidal Power Device Will Soon Begin Testing Off Scotland

Photo, posted May 18, 2017, courtesy of Chris via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Mangrove Trees And Climate Change | Earth Wise

July 7, 2020 By EarthWise Leave a Comment

Mangrove trees are small trees that grow in coastal saline or brackish water at tropical and subtropical latitudes. Many mangrove trees can be identified by their dense tangle of prop roots. These roots make the trees appear as if they are standing on stilts above the water. The tangle of roots allows mangrove trees to handle the daily rise and fall of tides and to slow the movement of tidal waters.

Mangrove forests provide many ecosystem services, including stabilizing the coastline by reducing erosion from storm surges, waves, and tides. The intricate root system of mangrove trees are attractive to fish and other species seeking food and shelter from predators. Mangrove forests also store large amounts of carbon.

But according to a new study recently published in the journal Science, mangrove trees won’t survive sea level rise by 2050 if greenhouse gas emissions aren’t reduced.

Using sediment data from 78 locations over the last 10,000 years, an international team of scientists led by Macquarie University in Australia estimated the chances of mangrove trees survival based on the projected rates of future sea-level rise.

When sea level rise rates exceeded 6 millimeters per year, which is similar to estimates under high-emissions scenarios for 2050, researchers found that mangrove trees were unlikely to keep pace with the rising water levels. But when the annual increase was 5 millimeters or less – which is the projected low-emissions scenario this century – mangrove trees are much more likely to survive.

These findings underscore the importance of reducing greenhouse gas emissions to mitigate rapid sea level rise. The future of mangrove trees may depend on it.

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Mangrove trees won’t survive sea-level rise by 2050 if emissions aren’t cut

Photo, posted December 17, 2012, courtesy of Edward Stojakovic via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Harvesting Blue Energy | Earth Wise

February 7, 2020 By EarthWise Leave a Comment

There are various ways to generate renewable energy from the world’s oceans, most obviously from the power of tides and waves. But there is also an oceanic energy source called osmotic or “blue” energy. Osmotic energy uses the differences in pressure and salinity between freshwater and saltwater to generate electricity.

When freshwater and saltwater are mixed together, large amounts of energy are released. If the freshwater and seawater are then separated via a semi-permeable membrane, the freshwater will pass through the membrane and dilute the saltwater due to the chemical potential difference. This process is called osmosis. If the salt ions are captured completely by the membrane, the passing of water through the membrane will create a pressure known as osmotic pressure. This pressure can be used to generate electricity by using it to drive a turbine. This has been demonstrated to work as far back as the 1970s, but the materials we have to use are not adequate to withstand ocean conditions over the long term and tend to break down quickly in the water.

New research, published in the journal Joule, looked to living organisms for inspiration to develop an improved osmotic energy system. Scientists from the U.S. and Australia combined multiple materials to mimic the kind of high-performance membranes that are found in living organisms. They created a hybrid membrane made from aramid microfibers (like those used in Kevlar) and boron nitride. The new material provides both the flexibility of cartilage and the strength and stability of bone.

The researchers believe that the low cost and high stability of the new hybrid membrane will allow it to succeed in volatile marine environments. They also expect the technology will be both efficient and scalable.

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