Managing Tropical Coastal Seas for 21st Century Challenges

Over 1.3 billion people — one fifth of humanity — mostly in developing countries, live in coastal communities bordering tropical seas. These waters host a wide array of ecosystems that are subjected to an equally diverse set of human impacts by societies with different traditions, beliefs, expertise and governance styles. Many of these communities depend greatly on coastal ecosystems for food and livelihoods.

It is now uncertain whether these very ecosystems can continue providing the crucial goods and services such communities need. On top of local stressors like overfishing and pollution, coastal seas now suffer from warming, ocean acidification, and catastrophic weather events directly related to our releases of greenhouse gases, particularly CO2. Climate change and associated impacts between now and 2050 will exacerbate the stresses on tropical seas, even as rapidly growing coastal communities demand more of the oceans’ goods and services.

Despite the clear benefits of sustainably managed coastal seas, the widespread goal of improved coastal management remains thwarted by fragmented, intermittent and unsuccessful approaches and practices, and, in many places, by a belief in simple technological ‘fixes’ without structural changes to management. Continuing to promote the same types of interventions and short-term development assistance is not going to result suddenly in success.

With the continuing growth in coastal aquaculture, the pressure to improve management of coastal ecosystems may seem lessened but it is not the same communities (nor as wide a range of individuals) who profit from aquaculture. Food security thus remains an urgent issue. Many aquaculture operations currently degrade natural habitats and ecological processes, putting coastal communities and economies at risk from loss of fishery production, shoreline stabilization, hazard mitigation and pollution filtering. Burgeoning coastal populations, growing international trade in fishery products, and climate change simply ensure that current management approaches are becoming ever less effective.

Southeast Asia

Fishing village in Southeast Asia. Photo: © Yvonne Sadovy de Mitcheson.

A new way forward

While global efforts might reduce the effects of greenhouse gas emissions and rising socio-economic status may slow population growth, whether tropical nations are bordered by sustainable coastal ecosystems or substantially degraded ones in 2050 will be determined by the effectiveness of local management. This is what my colleagues and I conclude in our recent research published in the Marine Pollution Bulletin.

While there are a few exceptional places, all too often current management of development, habitat degradation, pollution and overfishing is seriously inadequate. And if this management is not improved we are confident in stating the following:

  1. Most coastal fisheries will be chronically overfished,
  2. Loss of reef habitat will reduce capacity for fisheries production and further strain food security.
  3. Land-based pollution will increase to the extent that hypoxia and harmful algal blooms are routinely present.
  4. Pressures of coastal development will combine with sea level rise and more intense storms to further intrude on and erode natural coastlines, severely reducing mangrove, salt marsh and sea grass habitats.
  5. The cost of dealing with these impacts will further strain coastal economies and the future for people on tropical coasts in 2050 will be substantially more bleak than at present.

Management — of coastal development, habitat, water quality, biodiversity, or fisheries — requires locally focused interventions to change human activities and lower impacts, all coordinated across ecologically appropriate spatial scales.


Fisherman in his boat in Fiji. Photo: © Yvonne Sadovy de Mitcheson.

In the past, a great deal of management effort focused on the use of no-take marine reserves and other marine protected areas (MPAs). Suitably placed and sized MPAs can help sustain multi-species fisheries and reduce the broader ecosystem impacts of fishing where such effects are a major concern, although MPAs are not effective tools for addressing pollution, inappropriate coastal development and many other issues. Further, while some MPAs have proven effective in stemming biodiversity loss, maintaining fish populations and keeping habitats physically intact, the vast majority of MPAs around the world are not as effective as hoped, due to a failure to enforce, and a lack of compliance with, regulations that govern their use.

Suitably placed and sized MPAs can help sustain multi-species fisheries and reduce the broader ecosystem impacts of fishing, but MPAs are not effective tools for addressing pollution, inappropriate coastal development and many other issues.

MPAs are perhaps the most widely implemented spatial management measures and experience in designing and zoning MPAs or MPA networks could provide a major impetus for development of the broad-based spatial governance that is needed as our uses of the coastal ocean intensify. However, the policy shift needed for more effective management will not come about simply through the designation of more MPAs unless these are embedded in broader, more systematic spatial planning and ocean zoning that can deal with a broader range of human impacts while fostering appropriate types of use. The mismatch between local scale establishment of MPAs and national or international scale policies and agreements aiming to conserve marine biodiversity, coupled with the natural tendency of administrative bodies to be insular, leads to piecemeal efforts.

Integrated coastal management or ICM, now subsumed within ecosystem-based management or EBM, is a set of contextual and design principles to accommodate the need for seamless, cross-sectoral, regional-scale care of coastal ecosystems. But while ICM has been discussed for over 20 years, examples of its effective implementation are rare, partially because of the lack of effective interaction across management agencies and among political jurisdictions.

Similarly, while it is increasingly recognized that management should be done at ecologically appropriate scales — including through a framework that identifies 64 large marine ecosystems (LMEs) — large-scale management efforts frequently fail to generate the essential buy-in (active support) by local communities and stakeholders that is necessary for success.

What appears to be needed is a technically simple set of procedures that can enforce a multi-scale perspective and a strongly holistic approach to management despite the diversity of agencies, stakeholders and goals inherent in any attempt to manage coastal waters on a regional scale. We propose making expanded use of marine spatial planning (MSP) and zoning as a framework that will apportion coastal waters for differing activities, while forcing a multi-target and multi-scale approach, and achieving agreed ecological, economic and social objectives.

The promise of marine spatial planning and zoning

Marine spatial planning (MSP) is a tool for objectively partitioning marine space among competing uses. It has been used in conservation planning, largely in developed countries. Use of MSP to facilitate prioritization of the full array of uses to which we subject coastal waters has received very little attention, yet our use of coastal waters is now sufficiently intensive to require such spatial planning.

Fishermen set a net in Jericoacoara, Brazil.

Fishermen set a net in Jericoacoara, Brazil. Photo: Iolanda Fresnillo. Creative Commons BY-NC-SA (cropped).

In tropical developing countries, effective coastal management must acknowledge the widespread dependence of poor and politically weak communities on the use of fish for food. Acknowledging this dependence on artisanal fisheries is pivotal to reconciling the largely separate agendas for food security and biodiversity conservation. MSP can accommodate both coastal fisheries and aquaculture in coastal waters while adjudicating the access conflicts between them and other legitimate uses of the coastal seas.

Beyond addressing food security challenges, MSP can be expected to help address the issues faced by managers of tropical coastal waters in several ways:

In proposing expanded use of MSP, we are not suggesting that spatial planning is a quick fix for the pernicious failures of coastal management to date. We are proposing a substantial reinvigoration of management, using MSP as a Trojan Horse that will jump-start the changes in management and policy that are needed. We would be naïve to imply that success will come easily. It will not.

Long-term and comparative studies have demonstrated that there is no panacea: success of management requires that appropriate technical knowledge be applied in a context-sensitive way that builds ownership and compliance. Fortunately, there now exist detailed guides for using specific management approaches and a growing consensus regarding best management practices based on evaluations of success in particular instances.

We are not suggesting that spatial planning is a quick fix for the pernicious failures of coastal management to date. We are proposing a substantial reinvigoration of management, using marine spatial planning as a Trojan Horse that will jump-start the changes in management and policy that are needed.

The general principles we describe in our research can inform a variety of management tools and frameworks. Applying these will be very challenging. Clear vision and a strong commitment to success will be needed. The establishment of novel management regimes is likely best done incrementally, building from existing sustainable practices and nurturing numerous local, bottom-up efforts, while integrating them across a wider region in a way that is ecologically justifiable and societally defensible.

This will require a long-term perspective and use of an adaptive planning process, linked directly to social and ecological monitoring. Those leading this process will need to sustain a wider regional, national or LME-scale goal and not be satisfied with achieving short-term improvement for single local communities. This is the case, even if their initial successes will be precisely these small-scale (frequently short-term) improvements in local communities. Until now, the spill-on effects of such successes have been minimal, and felt only at the local level. That is insufficient.

Stilt fishing in Sri Lanka.

Fishing in Sri Lanka. Photo: Jared Hansen. Creative Commons BY-SA (cropped).

The MSP approach we propose will help leaders make the leap towards more strategic, systematic and region-wide improvements in sustainability. Refocused MSP, based on a spatially integrated index of human impact, offers a means to reconcile the multiple demands for use of tropical coasts, allowing developing countries to fulfill their needs and aspirations for fishing, aquaculture, industry, trade, tourism and conservation.

Long-term socially acceptable sustainability of tropical coastal seas based on expanded MSP will require policy that is effectively adapted to local societal, cultural and governance traditions, as well as effective and sustained participation of all community groups, strong local and national political leadership and vigorous support by development partners and NGOs. Urgent global efforts to reduce greenhouse gas emissions are also needed.

Humanity has the capacity to substantially improve coastal management; the futures of millions of poor people living on tropical coasts depend on us collectively rising to that challenge.


Read the full paper, “Transforming management of tropical coastal seas to cope with challenges of the 21st century”,
in the Marine Pollution Bulletin. You can also visit the UNU-INWEH website to view other recent publications, or check out Prof. Sale’s blog.


Prof. Peter Sale is a marine ecologist with over 40 years experience in tropical coastal ecosystems, particularly coral reefs. He is senior advisor to the director of the UNU Institute for Water, Environment and Health (UNU-INWEH). Prior to UNU-INWEH he was a faculty member at the University of Sydney in Australia, University of New Hampshire in the US, and University of Windsor, Canada, where he remains Professor Emeritus. His work has focused primarily on reef fish ecology, most recently on aspects of juvenile ecology, recruitment and connectivity. He has done research in Hawaii, Australia, the Caribbean, and the Middle East and visited reefs in many places in between. He has successfully used his fundamental science research to develop and guide projects in international development and sustainable coastal marine management in the Caribbean and the Indo-Pacific. His laboratory has produced over 200 technical publications and he has edited three books dealing with marine ecology.