Mangroves help raise hundreds of billions of fish annually

At first glance, mangroves might appear as quiet coastal sentinels, swaying gently between land and sea. But beneath the surface, these tangled root systems harbor a world that is teeming with life. For centuries, coastal communities have fished and foraged in mangrove-rich waters, relying on their resources to survive.

Today, new research reveals the extent of that support. A global study led by Philine S. E. zu Ermgassen and colleagues from the University of Edinburgh offers one of the most detailed estimates yet of the role that mangroves play in sustaining marine life.

The findings are staggering. Each year, mangroves nurture over 700 billion juvenile fish and invertebrates from commercially important species. These include prawns, finfish, crabs, and bivalves.

While this abundance doesn’t automatically translate into food on our plates, it highlights the irreplaceable role that mangroves play in ecological and economic systems worldwide.

Mangroves feed fish and support jobs

Food from oceans and coasts supplies essential nutrition to billions of people. The growing global population intensifies pressure on these systems. An estimated 260 million people currently earn a living from marine fisheries, and this livelihood is especially important in lower-income nations.

Fish stocks rely heavily on healthy ecosystems – mangroves included. When these environments deteriorate due to overfishing or habitat loss, the ripple effects reach dinner tables and job markets around the world.

Mangrove forests flourish in the intertidal zones of tropical and subtropical coasts. Their structure offers shelter and food to juvenile fish and shellfish. These nurseries are more than a convenience – they are an essential requirement for many species to survive their early life stages.

Small-scale and export-oriented fisheries alike benefit. Species such as crabs and shrimp fetch high market prices, especially in times of economic instability.

“While abundance at the early life-history stage does not directly equate to potential economic or biomass gains, this estimate indicates the critical role of mangroves globally in supporting fish and fisheries,” noted the researchers.

Mangrove life across the globe

To reach these conclusions, the team compiled data on 37 commercially important species. They included juvenile finfish, prawns, crabs, and a single bivalve species.

Data came from 481 field measurements spread across various geographies, though some regions, like West Africa, lacked sufficient information. To bridge the gaps, the researchers used the Delphi technique – an expert consensus method – to identify the ecological drivers of species density.

Twelve environmental variables shaped the predictive model. These included sea surface salinity, tidal amplitude, mangrove area, and net primary productivity. The model also factored in mangrove edge length and changes in forest extent.

Using global geospatial layers, researchers estimated species density across all known mangrove regions. This allowed them to visualize not just where mangroves exist, but where they produce the highest abundance of life.

Their findings revealed hotspots in Southeast and South Asia, the Red Sea, the Caribbean, and the northern coast of South America. Regions with deltaic mangroves – formed around river mouths – supported especially high densities.

Fish and crab numbers change by region

The study uncovered wide variations in abundance based on geography. Southeast Asia stood out, supporting nearly half of the global total.

Finfish and prawn numbers dominated in this region, with Indonesia alone producing 185 billion individuals annually. Countries like Myanmar, Malaysia, and Papua New Guinea also ranked high.

In the Americas, the focus shifted to crabs. Two species – Ucides cordatus and Ucides occidentalis – showed high densities in Brazil, Venezuela, and Colombia. These crustaceans not only play ecological roles but also hold cultural and economic significance for coastal communities.

Three species of penaeid prawns, which rely heavily on mangrove nurseries, had the highest predicted densities in places like Pakistan, India, Myanmar, and Viet Nam.

In contrast, some areas like the Pacific coasts of the Americas featured fewer finfish but boasted dense populations of the bivalve Anadara tuberculosa. This species, which is tied closely to red mangrove root habitat, contributes heavily to regional fisheries.

Some mangroves grow more fish than others

Geomorphic settings – such as whether the mangroves are in a delta or on an open coast – significantly influence fish and invertebrate densities.

Deltaic mangroves, rich in nutrients and tidal activity, supported the greatest abundance. On the other hand, fragmented mangrove areas or those with long edge lengths sometimes showed reduced productivity, possibly due to habitat degradation.

“Hotspots of finfish density include the extensive mangrove coastline of Brazil to the east of the Amazon, the Orinoco Delta, Venezuela, as well as the deltaic and lagoonal Caribbean coasts of Colombia and Mexico,” stated the authors.

While some models showed positive links between edge length and catch sizes, this study found a negative correlation. Fragmented edges may not provide the same protective benefits for juveniles as continuous habitats do. This suggests that mangrove quality – not just quantity – matters.

Fishers rely on mangroves

One of the most illuminating parts of the research was the comparison between fish abundance and fishing pressure.

Areas in South and Southeast Asia, such as the Mekong Delta, revealed strong overlaps. These regions host both high fish densities and large populations of small-scale fishers. In contrast, places like the northern Red Sea showed high productivity but low fisher numbers.

Some countries showed an inverse relationship. They had high numbers of fishers but lower estimated fish abundance. This mismatch could indicate overfishing or degraded habitats. Other areas, including parts of Australia and the Western Caribbean, supported recreational fisheries rather than subsistence or commercial ones.

This kind of data becomes vital for designing policies. It helps governments and conservation groups decide where interventions are most needed – be it through habitat restoration or fishery regulation.

Mangroves boost national food systems

The study found a clear correlation between a country’s mangrove-related abundance and its total ocean-derived food production.

In countries like Indonesia and Brazil, mangroves significantly contribute to national food systems. But in nations with limited mangrove areas – like Japan or Peru – their share remains small despite high overall seafood output.

Mangroves supply more than just protein. They underpin local economies, support employment, and offer buffers against environmental crises. In island nations, up to 80% of species targeted by fisheries depend on mangroves during part of their life cycle.

“Despite their relatively small area, mangrove-associated fish and invertebrate species can contribute substantially to fisheries catches,” the experts noted in their paper.

Losing mangroves means losing fish

The study emphasizes that mangroves must be treated as vital infrastructure for global food systems. While the 735 billion juvenile fish and invertebrates nurtured each year represents only a subset of all commercial species, it still showcases the immense productivity of these habitats.

If anything, this number is a conservative estimate, limited by data gaps in places like West Africa.

Areas with both high fishing pressure and low abundance signal urgent need for protective action. In contrast, regions with rich mangroves but low exploitation may offer opportunities for sustainable fisheries expansion. Knowing which is which allows better planning.

“Clearly, overall abundance of commercially important fish and invertebrate species is strongly influenced by overall mangrove extent,” the authors concluded.

Moving forward with clarity

The study bridges a long-standing gap in marine ecology. It doesn’t just describe what mangroves offer – it maps the benefits, models them, and links them directly to livelihoods. For policymakers, fishers, and conservationists, this is a crucial toolkit.

Protecting mangroves is more than just an environmental goal – it’s a necessity for maintaining food security and income in vulnerable regions.

With growing climate risks and population demands, mangrove forests must no longer be an afterthought. They are a living engine of resilience, quietly holding up a large part of the world’s coastal economies.

The study is published in the journal Communications Earth & Environment.

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