Fish Need Trees

This World Habitat Day, let’s celebrate the bridge between land and sea — mangroves trees. 

In the world of vibrant coral reefs teeming with fish, trees might be the last thing on your mind. But below the surface, mangroves play a vital role in supporting our underwater ecosystems as well as mitigating climate change. 

There are about 80 species of mangrove tree. From Red Mangrove (Rhizophora mangle) recognizable by its distinctive stilt-like roots that provide stability and support in muddy, tidal zones. Black Mangrove (Avicennia germinans), White Mangrove (Laguncularia racemosa), typically found in slightly higher, less waterlogged areas compared to red and black mangroves. It has glandular leaves that excrete excess salt and Buttonwood Mangrove (Conocarpus erectus) are just some of them.

Mangrove trees are uniquely adapted to survive in brackish and saltwater environments, with their root systems enduring periods of submersion in seawater. While their specialized roots can handle these saline conditions, as well as frequent flooding, their canopies grow above the waterline. It is as if they grow  half in and half out of the salty water line. 

Climate Change and Greenhouse Gasses

As most people know, trees are critical in reducing carbon dioxide (CO₂), through photosynthesis.  All trees, plants and algae absorb CO₂ during this process and convert it into oxygen and organic matter.  Phytoplankton in the oceans are also carbon sinks. 

This is critically important as CO₂ is the primary driver of climate change and is known as a greenhouse gas.  When we burn fossil fuels, oil, gas and coal, we release CO₂ into the atmosphere which increases the concentration of greenhouse gasses. These gasses trap heat by absorbing infrared radiation that the Earth’s surface emits and re-radiates it back toward the surface, thereby warming the planet.

As CO₂ levels rise, more heat is trapped, intensifying this greenhouse effect and subsequently increasing global warming. Our CO₂ absorbing forests, algae, mangroves, and phytoplankton therefore play a crucial role in combating climate change and mangrove trees are the unsung heroes of this process because they are carbon dioxide guzzlers. 

Coastal Powerhouses

What makes mangroves trees truly special are their root systems that are often exposed and tangled, and which serve as networks that can stabilize coastlines, filter pollutants, and most importantly, act as carbon sinks. 

Mangrove trees have exceptional carbon sequestration abilities. They absorb and store large amounts of carbon dioxide from the atmosphere during photosynthesis and trap it in their biomass, roots, branches, and leaves, as well as the carbon-rich sediments beneath them. But mangroves annually collect carbon at a rate ten times greater than mature tropical forests. 

Fish Nurseries

Beyond their super hero-like ability to absorb greenhouse gasses, mangrove trees offer another invaluable service – their root systems provide a safe haven for more than 1500 other species. Of the aquatic species they benefit, including birds, algae, and mammals, the connection between fish and mangroves is arguably the most essential. 

Before migrating to open water and large coral reefs, many species like sharks, barracuda, tarpon, snappers, groupers and snook, among many others, need a safe protected space to mature, that is free from strong currents and predators. The tangled root systems of the mangroves, submerged underwater, are perfect fish nurseries. 

When the rainy season arrives, the increased flow of freshwater introduces freshwater species into the mangrove fish nurseries, while in contrast, during the dry season, the lower salinity levels drive many marine species to migrate further offshore. Certain marine fish species, such as the snook fish, prefer the lower salinities of the mangroves and choose to stay there throughout the year.

Our fish populations need these special coastal ecosystems to thrive, and so do local human populations who rely on the mangrove trees not just to mitigate climate change but also for important fruit and seed harvests as well as for healthy fish populations. Please consider donating to The Canopy Project so that we can keep planting these special trees, every single mangrove planted, matters.

Karuna Singh, Regional Director – Asia, EArth Day Network India

The health of coral reef fish species populations and the success of mangroves are unquestionably linked. Researchers at the Bulletin of Marine Science concluded that diminishing adult fish populations from coral reefs are directly correlated to the disappearances of the world’s mangrove populations. 

Asian countries are home to the largest mangrove populations, at about 42 percent. China, India, and Indonesia are the top three countries with the highest fish production, making Asia known for both mangroves and fish. In India, EARTHDAY.ORG has been planting mangrove trees with local partners on the ground for many years now in the Sundarbans riverine estuaries of Bengal. In the U.S., Florida’s coasts are home to the largest mangrove swamps, encompassing over 600,000 acres of critically important habitat for wildlife.

A Crucial Battle

Despite their critical importance, these forests continue to decline across the world. The Philippines has lost more than 10 percent of their mangrove coverage since 1990 and Nigeria has seen a detrimental loss of nearly 161.9 km squared.  Nearly all of the 70 different mangroves species face destruction due to water pollution, dredging and ironically climate change.

Although projected to survive a moderate rising in sea levels, an extreme sea-level rate, driven by melting ice and thermal expansion, can inundate mangrove areas. This will disrupt their delicate balance and potentially lead to loss if the mangroves cannot migrate or adapt quickly enough. 

Increased temperatures can stress mangrove trees, heightening salt stress and affecting growth. Altered precipitation patterns may result in either excessive flooding or droughts, both of which can harm mangroves by altering salinity levels and water availability. 

More intense storms can cause physical damage to mangroves, uprooting trees and disrupting sediment balance, while ocean acidification weakens root structures and impacts dependent marine life. 

Mangroves are a great example of how critically important each and every part of an ecosystem is. We need to educate people about why these special trees are so critically important to the health of the planet and why fish need them!

Emily Walker, Education Coordinator, EARTHDAY.ORG

A Cycle of Human, Fish, Tree Dependence

It’s simple.  Humans rely on fish for food and livelihood, fish depend on mangroves for critical habitat and nursery grounds, and mangroves depend on us for protection and conservation.  Without mangroves to help fish flourish, fish populations will decline, affecting the food security of over 200 million people in coastal regions.  A staggering estimated 75 percent of commercially caught fish can be traced back to these coastal forests.  

Which is why we must recognize and preserve the bond between fish and mangrove trees, ensuring the survival of both, for generations to come. You can be part of the efforts by donating to The Canopy Project, EARTHDAY.ORG’s worldwide reforestation efforts.