Understanding how mangrove loss threatens biodiversity

People boating in mangrove forest, Malaysia, Asia

Marine and coastal ecosystems play a crucial role in keeping people and the planet healthy. They are home to millions of species, provide water, food, livelihoods and energy to millions of people and help reduce the magnitude and impacts of climate change. 

Although global awareness and action for ocean habitats is growing, our vital “blue ecosystems” remain threatened by rising temperatures, pollution, over-exploitation and coastal development.

New international targets for nature – agreed in December 2022 as part of the Kunming-Montreal Global Biodiversity Framework – stress the urgent global action needed to safeguard blue ecosystems, with targets to protect and to restore 30 per cent of the world’s marine and coastal ecosystems by 2030, as well as acting to safeguard and ensure sustainability in the use of marine biodiversity. The UN Sustainable Development Goals also underline the crucial need to protect and sustainably manage our ocean ecosystems to ensure a future for people and the planet.  

Today, the UN Environment Programme (UNEP) launches an exciting new interactive website that dives into four important marine ecosystems – kelp, coral reefs, seagrass meadows and mangroves – showcasing the latest scientific research on the health of these areas and the benefits they provide to nature and society.  

Ahead of the launch of the Deep Dive visual feature, UNEP-WCMC marine experts – alongside research partners from Wetlands International, Manaaki Whenua Landcare Research and the universities of Cambridge and Aberystwyth – worked on a special report exploring changes in mangrove coverage since the mid-1990s, highlighting areas of both loss and of encouraging restoration, and what these changes could mean for people, carbon storage and the thousands of wildlife species dependant on and associated with mangrove habitats.

Scoping how changes in mangrove coverage impacts nature

The analysis led by UNEP-WCMC combined latest mangrove data from Global Mangrove Watch with a series of other data and modelling on fishing locations, biomass carbon and the distribution of mangrove-dwelling wildlife.

It found that between 1996-2020, global mangrove coverage decreased by 3.4 per cent – or 5,245 km2 – however, encouragingly in recent years mangrove decline has stabilised, with gains around many of the world’s large rivers, estuaries and deltas offsetting further losses.

As well as assessments on carbon storage and global economic reliance on mangroves, the team conducted the first-ever spatial assessments into the potential impact habitat loss has had on mangrove associated species around the world.

To-date, the link between mangrove ecosystems and the wildlife they support and services they provide has not been well studied – our new analysis gives a first look at how changes in mangrove extent is impacting on biodiversity, carbon and fisheries.

Dr Chris McOwen, report lead author and UNEP-WCMC Lead Marine Scientist

Using best available global wildlife data from the International Union for Conservation of Nature the analysis found that 1,533 species are associated with mangroves, with nearly half of relevant mangrove-associated mammals, 22 per cent of fish, 16 per cent of plants, 13 per cent of amphibians and eight per cent of bird and reptile species threatened with extinction. The risk of extinction is also rising for 44 per cent of these species.

The team identified areas which had both a high number of species associated with mangrove forests and which had undergone high rates of change in mangrove extent. They found that:

  • For marine vertebrates – species ranging from fish, turtles, whales, dolphins, porpoises, otters, seals, crocodiles, alligators and manatees – the Asia-Pacific and Americas (especially Indonesia, the USA, Ecuador and Cuba) are predicted to have experienced highest changes (gain and loss) in species between 1996 and 2020.
  • For terrestrial vertebrates – from frogs to lizards, snakes, bats, monkeys, sloths, tigers and rodents - the Asia-Pacific (Indonesia and Australia in particular) and Mexico and Cuba are predicted to have experienced the greatest species changes.
  • For plants – from “true” mangrove trees and shrubs, to orchids, vines and salt-tolerant herbs, shrubs and climbers – Indonesia, Australia and American territories – including Panama, Brazil and Colombia – were found to be especially important habitats, with the greatest losses in plant species estimated to be in Indonesia.  
  • For more than 1,000 bird species – ranging from dependent species such as the Bended Rail in the Pacific region, to migratory visitors such as herons – the Asia-Pacific was found to be especially important, but with high species loss seen in Indonesia. Several countries across the Americas and Africa are also of high importance, and Ecuador has seen a large boost as a hotspot for avian biodiversity, potentially linked to increases in mangrove area in and around the mangrove-dense Manglares Churute Reserve.

The team hopes that their analysis of how mangrove change is linked to biodiversity importance will inspire further work to strategically prioritise mangrove conservation and restoration. For example, they highlight the Indo-Malay Philippine Archipelago, which has the highest diversity of mangrove species and one of the highest rates of mangrove loss.

To ensure global targets and efforts to protect and restore natural ecosystems really do benefit nature, we need ongoing investigation to understand what the consequences of our actions to conserve, restore and sustainably use habitats like mangroves means for species.

We hope our analysis will encourage ongoing research to deepen our understanding of the relationship between mangroves and nature, and to help prioritise restoration efforts.

Dr Chris McOwen, report lead author and UNEP-WCMC Lead Marine Scientist

Progress on mangroves depends on harmonised action

The report outlines key recommendations to strengthen knowledge of mangrove health, use and management, and to ensure cohesive management and restoration activity at local scales.

It calls for improved local-level data collection, education and inclusive collaboration, as well as better data on the effectiveness of mangrove site management, and the development of standardised reporting for mangrove forest health. They also urge leaders and policy makers to ensure mangrove protection and restoration are integrated into joined-up conservation strategies.

I hope that this publication will serve to inspire governments around the world to embrace mangroves as a nature-based solution and to take action to protect, restore, and sustainably manage the magical mangrove forests that provide vast ecosystem services for nature, people and the planet.

Leticia Carvalho, Head of Marine and Freshwater Branch, UNEP

  • Discover more about mangrove coverage and biodiversity, along with other crucial blue ecosystems, via the new UNEP Deep Dive visual feature.
  • Find out more about the distribution of various marine habitats around the world – including mangroves, corals, seagrass meadows and saltmarshes – and the extent of their inclusion in protected areas via UNEP-WCMC’s Oceans+ Habitats platform.

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