Skip to content

Zone Tropical Coastal Oceans; Manage Them More Like Land


Lots of People Live Along Tropical Coasts

We appear to have been always a coastal species.  If we define ‘coastal’ as ‘within 100 km of a coastline’, then the coastal strip comprises 21% of all land, but is currently occupied by 2.6 billion people, 37% of humanity.  If we limit attention to the tropical coastal strip, 1.36 billion of us, 20% of all humanity, currently live on just 7% of all land, at densities that average twice as great as in inland areas.  Nine of the world’s 19 megacities, larger than 10 million occupants, are tropical coastal cities.  These numbers are part of a recently published study by a geographically broadly distributed group of scientists I had the pleasure of leading.  They are based on 2011 demographic data.

Manila 1989 vs 2012 lo rez USGS and NASA credits

Landsat satellite images depict the growth of Manila between 1989 and 2012.  Covering 638 km2, its greater metro region now houses 11 million people, making it the 9th largest city by population.  One fifth of the global population occurs along tropical coasts in small villages and in cities like this.  Image courtesy U.S. Geological Survey – Earth Resources Observation and Science Center, and National Aeronautics and Space Administration – Land Processes Distributed Active Archive Center

Using available data on demographic trends, we determined that by mid-century, 2050, the tropical coastal population will have grown by 45% to 1.95 billion, living at an average density of 199 people per km2 (the present average density on tropical coasts is 141 per km2).  What happens along tropical coasts is of direct concern to a sizeable number of people, many of whom derive their livelihoods, and much of their food from the nearby ocean.

Sale et al Figure 1

Global population density emphasizing the coastal region (within 100 km of shore) based on LandScan 2011 data. Population density is greatest in the tropical coastal region, where 20% of the planet’s 7 billion people live on a mere 7% of Earth’s total land area at densities averaging 141 km-2.
Figure from Sale et al, 2014, Marine Pollution Bulletin.

Present Coastal Management Policies are Failing Globally

Conceived and funded primarily by Canada-based Institute for Water, Environment and Science, of the United Nations University, our project began with a small workshop held at the University of Queensland, Brisbane, Australia.  The team included fisheries scientists, conservation scientists, social scientists and an expert in marine law.  Most of us had wide experience in efforts to improve coastal management in the tropics and that experience came from around the world.  We looked critically at the status of tropical coastal waters and their fisheries, made reasonable projections to mid-century, and concluded that current procedures and level of effort to improve management of these coastal waters are seriously inadequate.  They are doomed to fail unless changed.

The fact is that coastal waters in the tropics have been being degraded by human activities for a very long time, just as is the case in temperate regions, and for much the same reasons – overfishing, pollution of various types from on-land activities, and inappropriate coastal development that leads to habitat destruction in coastal waters.  With growing populations the local stresses on coastal ecosystems all increase, making the task of managers more difficult year by year.  In addition, climate change and associated global impacts of humanity, most notably ocean acidification, are also creating stronger pressures on coastal waters.  Sea level rise, although happening slowly, forces ecosystems like salt marshes and mangrove forests, portions of the coastal fringe to migrate inland where that is still possible, and be squeezed into an ever narrowing range where our onshore development makes migration impossible.  Sea level rise also increases the potential damage to infrastructure due to tropical storms.  Acidification and warming are having growing impacts on many components of coastal marine ecosystems.  Most notably in the tropics, these impacts are making coral reefs less viable and the reef science community has been documenting the depressing deterioration of coral reef ecosystems for some time now.

One portion of our study was a look at the consequences for fishery production of the loss of corals on coral reefs.  It has been known for some time that many small reef fish species disappear, or become less abundant, following loss of coral.  We were able, using a modeling approach, to show that the changes in the reef ecosystem brought about by loss of coral also lead to a substantial reduction in the reef’s capacity to produce fishery species – those larger fish species that are major targets of coastal fisheries.

When one adds the environmental impacts of climate change and ocean acidification to the impacts of a growing human population, it is clear that stresses on coastal marine ecosystems are going to increase significantly through mid-century.  In other words, if our policies for managing these coastal ecosystems are inadequate now, they will be of even less use in future years.  We have to tackle the problem of how to manage the coastal ocean differently.


Throughout the tropics, as here in Indonesia, millions of people derive their food and livelihoods from the coastal ocean.  Photo © Yvonne Sadovy de Mitcheson

We Know Why Policies Fail and How to Fix This Problem

The final part of the article is about why current policies fail and what can be done about it.  The good news is that current failure is not because we lack the technology to fix most of the problems we observe.  We know how to reduce fishing pressure.  We know how to reduce pollution of coastal waters.  We know how to develop our coastal lands in ways that do not destroy the capacity of the coastal ocean to continue to be productive and healthy.  We even know how to avoid conflicts between such uses of the coastal ocean as fishing, aquaculture, conservation, tourism and commerce.  But we are failing, repeatedly, to put this knowledge to good effect.

The reasons for this failure are several.  First, there is a widespread tendency to fail to approach management in a sufficiently integrated manner, with a holistic view of what is to be achieved.  Instead, we attempt to manage fisheries without reference to the impacts of pollution on the ecosystem the fish live within.  Or we manage water quality, without regard to the impacts of overfishing and habitat destruction.  Or, worst of all, we assume that climate change will have very deleterious impacts, and, feeling hopeless, we cease to pay any attention to local causes of habitat degradation, believing it’s not worth worrying about.  This tendency to tackle specific aspects (or none at all) rather than the whole problem is encouraged by the administrative structure a government has set up – separate agencies for fisheries, conservation, ports & harbors, and so on.  The tendency can be overcome, but only if there is leadership with vision to see the need to work more holistically.

Second, there is a great tendency to do things at too small a scale in space or time.  Environmental management is really about managing our impacts so that the ecological system can operate successfully.  It follows that the change to our activities needed to change our impacts must be mounted at an ecologically appropriate scale, and preferably with boundaries that mirror real ecological boundaries rather than artificial jurisdictional ones.  To do this requires sometimes that management agencies collaborate with agencies in neighboring jurisdictions in order to be able, together, to manage a large coastal ecosystem.  Then too, changing our impacts on a coastal marine region always takes time, and only after our impacts are beginning to lessen can the ecological system begin to repair itself.  Ecological change has its own timeframe, sometimes quite short, but frequently quite long relative to human attention spans.  This means that the results of a reduction of our impacts may not be observable for decades, or even longer.  Planning a project that requires real ecological results within 3-5 years almost guarantees failure, simply because the effort has not been sustained for sufficient time.  Indeed, many current efforts, done at too small a scale and for too short a time period, yield small, good-news stories of local success, which lasts a few years and then withers because the project has finished, and the effort has not been institutionalized.

Third, technical experts often forget that real live humans are a part of the system their efforts are designed to change.  And humans have cultural, societal, religious and traditional belief systems that strongly influence their responsiveness to new ideas.  There are pervasive beliefs, in many social systems, that the ocean is so immense that we can never really harm it – there will always be fish to catch.  Or beliefs that the ocean is so large that we can always dispose of our waste materials safely in it – it is impossible to pollute coastal waters, because pollution discharged there will simply be diluted away.  These beliefs are very strong, in developed as well as developing communities, despite many examples of evidence to the contrary.  Just try telling a recreational fisherman in Florida that, actually, recreational fishing has measurable and serious impacts on the abundance of reef fish populations, and needs to be regulated!  The belief systems that are integral to a particular community must be accommodated in any plan to implement or improve coastal management.  This accommodation is not achieved by lecturing people on the need to change, by providing data on the reasons why change is required, or even by painting pictures of how their world will degrade if they do not change.  It is achieved by working with people, over long periods of time to build their understanding of the need, and their receptivity to the actions to be implemented.  Far too few coastal management programs devote enough time to this public outreach, education, and accommodation effort.

Fourth, and perhaps most important, many efforts to improve coastal management fail because there is an absence of truly committed leadership.  This leadership can exist within government, in an environmental management agency, in a local NGO dedicated to conservation, in a particular stakeholder group such as a coastal fishery cooperative, or a tourism association, but it has to exist somewhere for success to be possible.  In many places in need of improved coastal management, this leadership does exist, but it lacks the tools and the finance to have any effect.  Such places are ones ripe for making real improvements to the condition of their coastal ocean.  Other places may lack any evident leadership for environmental improvement, and if that is the case, efforts to make improvements there will likely fail.

Our article proposes a superficially simple approach to obtaining success in coastal management, given that appropriate leadership is available.  We suggest the use of marine spatial planning (MSP) as a Trojan horse.  MSP is an objective methodology for prioritizing and then partitioning a marine region among competing uses.  It has been used successfully in the conservation arena to build networks of marine protected areas, but we suggest its use can be extended as the procedure for what amounts to land planning of the coastal ocean.  We routinely zone land for different uses; it is time to begin to zone the coastal ocean in a similar way, and MSP could facilitate doing that.


We see Marine Spatial Planning as useful in its own right for ocean zoning, but also as a Trojan horse to insert the needed integrated, holistic perspective, and spatial and temporal scale at which to undertake coastal management.  Figure from Wikipedia Commons, after painting by Henri Motte

But in our view, this use of an objective zoning technique has its chief value in how it will solve the other major impediments to progress in coastal management.  To apply MSP in the sweeping way we propose would demand that administrative agencies collaborate effectively over time, would facilitate a more holistic view of the goal, would encourage an ecologically appropriate spatial and temporal scale of action, and hopefully would recognize the need to invest in understanding the needs, desires and beliefs of particular stakeholder groups.  In this way, MSP is a Trojan horse delivering a number of solutions to problems that were perhaps not even perceived at the time the decision to attempt to improve coastal management was made.

While our article paints a serious view of a degraded future for coastal populations throughout the world’s tropics, it does propose a workable approach for avoiding this future.  Yes, if climate change continues unchecked, life in many coastal regions will get a lot worse than it is now.  But if serious efforts are taken to correct the local causes of degradation, these coastal regions will be in far better shape than would otherwise be the case.  We know what the problem is, but we also know how to fix it.  The first step on that path is to recognize just how serious a problem it really is.  The second step is to get serious and appreciate that more of the same old approaches is just not good enough.  There is work to be done.