The diagnosis for the planet is clear. While a great many problems require more research, the focus of future research should expand dramatically to maintain and restore biodiversity rather than focus on, as coral reef biologist Nancy Knowlton has said, “further refining the obituary of nature.” Part of conserving biological diversity is identifying treatments. Scanning for solutions to environmental problems can give us a sense of the quantity and quality of solutions and the conservation priorities for a given set of problems as well as provide the groundwork for assessing each solution’s effectiveness.

To test the practicality and usefulness of solution scanning, we selected three main threats to the marine environment,1–4 where humans have overfished the majority of large fish,5 spread invasive species into almost every marine ecoregion,6 and created oceanic dead zones—where only a few species, such as microbes and jellyfish, survive due to high levels of agricultural runoff.7 We then undertook a comprehensive literature search and consulted widely with colleagues. We identified broad problems within each of these three areas as well as the range of generic and specific solutions (described in “Methods”). The aim of such an exercise is neither to identify specific policy needs8–9 nor to recommend solutions but to provide a list of the specific tools available to scientists, policymakers, conservationists, educators, and students. To see the complete list of these problems and interventions, click here.

What’s Seen in the Scan? Zoomed Out

Many of the problems seem grander than the solutions, which can seem marginal at best, even if they are not (e.g., washing footwear to prevent the spread of invasive species). Treatments also seem to be more frequent than prophylactics. Programs to locate and remove lost fishing gear, which can continue to fish indefinitely, seem to have positive effects on biodiversity, be cost-effective, and have bipartisan political support. But one might naturally ask, why is so much fishing gear allowed to be lost?

Another apparent trend is that the vast majority of solutions require governments to be involved at some level, especially for solutions that are preventative. A private company might be able to successfully manufacture a “supersucker”—an underwater vacuum that sucks up invasive algae—but private companies cannot prevent the spread of that same algae by regulating the market for aquaculture and preventing its disposal into natural settings.

The solutions we found range from the conceptually rudimentary, like the proposed use of insects to replace wild fish in feed for farmed fish, to the highly technical, such as microwave technology to treat ballast water. Some solutions are well established (e.g., quotas on fisheries catches) and have been extensively studied, while others, like marketing cloned omega-3 pork10 as a replacement for fish, are highly speculative and have attracted little methodical assessment.

We can also see considerable variation in the diversity of suggested solutions—perhaps due to a solution’s ease of implementation or the concern that an issue has generated. For instance, scientists have generated a wide range of options for dealing with seabird bycatch but have fewer suggestions for ameliorating the actual damage that trawling does to coral habitats.


Gavin Newman/Greenpeace
Greenpeace divers in the Philippines

It would be useful to know to what extent, if at all, various interventions are being carried out. For example, the research problem is no longer whether ballast water spreads invasive marine species; we know it does. The question now is what percentage of the global shipping fleet is doing something to address the issue? In a similar vein, what percentage of the global long-lining fleet uses streamer lines to deter seabirds? What percentage of the global fishing fleet has humans or computers onboard observing fishing practices?

We believe that compiling an issue’s possible solutions will not only lead to further evaluation but also to the generation of further ideas. It should also lead to the identification of gaps in any such list.

What’s Seen in the Scan? Zoomed In

One of the proposed solutions to overharvesting in the oceans is to reduce demand for unsustainable species and encourage demand for sustainable ones, in hopes that changing demand will change supply.11 In scanning all the solutions for overharvesting, we can see that many—such as boycotts, certification, seafood guides, and substitute products—are directed at consumers. These are some of the only tools that do not involve producers (i.e., the fishing industry itself). The scan shows us that, if you are not part of the fishing industry or the groups that regulate them, these are some of your only options for direct engagement in the issue of overfishing.

Tools that rate the conservation consequences of eating different fish certainly influence the behavior of some, but this effect seems masked by growing overall demand; we see no decrease in demand for overfished species. However, only one experiment to date has tested the impact on seafood sales of consumer-targeted conservation measures. Researchers examined the effectiveness of red, yellow, and green signs that indicated sustainability of seafood species in a chain of grocery stores in San Francisco. Comparing the two stores that introduced the signs to eight stores that did not, they found that sales of green-tagged “best choice” seafood increased by 29 percent per week, sales of yellow “proceed with caution” seafood sales decreased by 27 percent per week, but the sales of the red-tagged “worst choice” seafood, the heavily overfished species, remained the same.12

A likely explanation for why sales of the red list species stayed the same is that there were few substitutes for those species. While, as consumers, we have responded to an ethic opposed to animal cruelty and factory farming with garden burgers, fake chicken strips, and tofurky, there are no equivalent products for seafood. Scientist might have cloned a pig with omega-3 fatty acids, but soymon and tofuna are nonexistent.

Are the Solutions Really Solutions?

The solution scan is just the first step. The next step is to ask how much each solution costs and how well it works.13 Determining effectiveness is the overarching goal of the Conservation Evidence project (, which is building a comprehensive summary of the effects of conservation interventions for all biodiversity globally, just as the medical field did 30 years ago when it began systematically reviewing treatments and recoveries.


Raquel Del Diego/Greenpeace
Greenpeace divers collected about 3,500 kilograms of garbage from the seabed in a maritime national park in Cabrera, Spain.

This program includes an open-access journal (eponymously named Conservation Evidence) that encourages the monitoring of interventions, a database of summaries of peer-reviewed papers that assess a particular conservation intervention, and the production of synopses that summarize the information for a particular subject. The first synopsis identified and assessed 59 possible conservation interventions to maintain or restore global wild bees.14 Other synopses are underway for birds, European farmland, grasslands, and butterflies.

Just like medical remedies, some interventions work, others don’t, and some have potential side effects that warrant consideration. Chicken soup seems to be genuinely effective in treating the common cold, while antibiotics don’t work at all. Cold medications are fine for adults but dangerous for small children. Acetaminophen can cause liver damage if taken in doses that are too high. Zinc nasal sprays can permanently damage one’s sense of smell.

The solutions that exist for overfishing show a variation in usefulness, including likely differences in effectiveness for different areas or taxa. Establishing marine protected areas has resulted in increased biomass and abundance for many species but fewer positive effects for protecting migratory species. In some cases, marine protected areas even improve adjacent fisheries. However, no-take fishing areas still comprise less than one percent of the global ocean.15 Continued research on the Great Barrier Reef suggests that the abundance of sharks is higher in complete no-entry zones than in simply no-take zones.16 Similarly, government programs to buy back boats from the fishing industry do not always lead to a reduction in overall fishing capacity.17 Turtle excluder devices on shrimp trawlers might work in principle, but fishermen in Mexico are known to tie them shut.18

There can be a range of side effects to interventions. For example, shark liver oil does deter seabirds, but obtaining shark oil may generate its own problems until the active ingredients of the oil can be synthesized. In addition, the cost of solutions varies considerably, for example, from establishment and maintenance of marine protected areas to changing the line color for long-lining.

What’s Missing?

In addition to these considerations, consider what these lists of solutions exclude. It is worth noting the latent state of research related to solutions to climate change and increased carbon dioxide levels in the oceans. Acidification is likely to have substantial effects on coral reefs and other calcifying organisms and, yet, one of the only solutions we have seen mentioned is to facilitate grazing by herbivorous fish and invertebrates on coral reefs to outcompete algae.19 In response to rising sea surface temperatures, there have been discussions about transplanting heat-tolerant zooxanthellae to corals.20 Similarly, in response to rising sea level, researchers have proposed transplanting corals, seagrasses, and other important benthic species in shallower water to facilitate habitat shift. Some geoengineering proposals to sequester carbon dioxide also involve and potentially will affect marine biodiversity, such as iron fertilization.21

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We also were not certain how to categorize some direct human impacts on marine biodiversity. One notable problem is ship collisions with marine mammals. One solution is to prohibit boats in certain areas. Regulations and signs to reduce speed might also work, although only with proper enforcement. A more innovative solution has been implemented for endangered North Atlantic right whales: buoys that listen for whale calls ( and alert boat captains to their presence. But it is unknown how effective this will be.

Similar to the medical profession, the process of solving conservation problems does not end with selection of appropriate interventions. Ideally, the process is adaptive and iterative, beginning with scanning solutions, including new tools as they become available, and then reviewing the evidence for effectiveness, selecting interventions, evaluating effectiveness, and adjusting accordingly.


We compiled our lists of solutions according to the following structure:

Broad problem: The generic issue that needs solutions (for example, capture fisheries).

1. Specific problem: The narrow issue that needs solutions (for example, bycatch of marine megafauna).

A) Broad solution: The general objective of the intervention (for example, reducing turtles caught in longlines).

I. Specific solution: The actual intervention that a practitioner may adopt. Examples include blue-dyed bait, hardware painted to remove metallic sheen, countershaded floats (blue on bottom, orange on top), or treated bait (e.g., with quinine, hydrochloride, habanero chili extract, urea, squid ink, cilantro, or sea hare ink).

We define problems in marine waters as those occurring in the open ocean as well as some problems that affect both open ocean and brackish, coastal, estuarine, and intertidal environments. While the challenges we discuss here apply across almost all of these environments, we do not include in our analyses all possible issues facing inshore environments, particularly those specific to salt marshes and mangrove ecosystems. In addition, we do not consider some problems that are unique to shallow waters but are not environment-specific, such as light pollution and thermal pollution. For invasive species, there are scores of potential human-mediated transport vectors in the ocean;6,22–24 we focus here on select vectors as examples of solution scanning.

We do not explore interventions that apply equally to all environments—freshwater, marine, and terrestrial—such as those that reduce the levels of greenhouse gases or increase general environmental awareness via education. We also exclude issues related exclusively to sociology and economics (e.g., the profitability of fisheries), unless they have an impact on biodiversity. We have not provided references for well-known interventions, such as increasing mesh size of fishing nets, but we have aimed to provide them for those conservation measures that might be unfamiliar to some readers. We do not include those that are as yet theoretical, such as in vitro seafood.

We recognize that these are still very broad problems that could be further refined (e.g., compliance could be broken down into all sorts of issues, such as illegal transshipments at sea, reflagging vessels, unplugging and breaking transponders, harassing observers, misreporting, underreporting catches, or keeping double log books). We also focus on tools rather than policies, although a scan of U.S. and international policy efforts would be an interesting area for future research.


Paul Hilton/Greenpeace
Greenpeace inflatables and two Greenpeace ships, the MY Arctic Sunrise and the MY Rainbow Warrior, take action against a Tunisian tugboat towing a cage of bluefin tuna to a tuna farm, where the fish are fattened and then sold.

For preventing and reducing invasive species and disease, we focus first on the different vectors of invasions and then turn to the species groups themselves and list more than 50 possible solutions. For pollution we summarize the main types: organic, inorganic, and toxic pollution from land-based activities; organic and chemical pollution from carnivorous mariculture; noise pollution; and nuclear pollution. We list more than 25 interventions that might reduce the extent of pollution or reduce its impact. We also list the 106 interventions for seven specific problems related to capture fisheries: overfishing of the target species, ghost fishing by lost or discarded fishing gear, indirect impacts of fishing on habitat and sessile organisms, bycatch of fish/discards, bycatch of marine megafauna, bycatch of seabirds, and compliance. All problems are listed with equal prominence, although they differ in scale and intensity. Similarly, all interventions are presented with equal prominence despite being obviously different.


We thank N. Knowlton and W. Swartz for reviewing an early version of this article, M. Huelsenbeck for his contribution, and the numerous colleagues who identified interventions. We also thank D. Croll and M. Bailey for their helpful reviews. The Pew Charitable Trusts funds the Sea Around Us Project, and Jennifer Jacquet. William Sutherland was funded by Arcadia.


Jennifer Jacquet

Jennifer Jacquet is a guest editor for the Oceans issue of Solutions. She is a postdoctoral fellow with the Sea Around Us Project at the University of British Columbia. She also teaches an undergraduate...


Ian Boyd

Ian Boyd is a professor in biology at the University of St Andrews. He is director of both the Scottish Oceans Institute and the Natural Environment Research Council’s Sea Mammal Research Unit. He has...


James T. Carlton

James T. Carlton is professor of marine sciences at Williams College and director of the college’s Mystic Seaport Maritime Studies Program. He is founding editor-in-chief of the journal Biological Invasions,...


Helen E. Fox

Helen E. Fox is a senior marine scientist with the World Wildlife Fund’s Conservation Science Program, providing technical and scientific support for the marine places where the fund works, with particular...


Ayana Elizabeth Johnson

Ayana Elizabeth Johnson is a marine biology doctoral candidate at the Scripps Institution of Oceanography. Her research focuses on the ecology and socioeconomics of coral reef fisheries management.


Laurence Mee

Laurence Mee is director of the Scottish Association of Marine Science, Scotland’s largest independent marine research institute. He leads the 15-country, 31-institution European research project KnowSeas...


Joe Roman

Joe Roman is a conservation biologist, author, and fellow at the Gund Institute for Ecological Economics and a McCurdy Visiting Scholar at the Duke University Marine Lab. He is the author of "Whale and...


Mark Spalding

Mark Spalding is a senior marine scientist at The Nature Conservancy, working out of the Conservation Science Group at the University of Cambridge. He specializes in global marine biodiversity assessments...


William Sutherland

William Sutherland holds the Miriam Rothschild Chair of Conservation Biology at the University of Cambridge. He is committed to changing global conservation practice through the development of evidence-based...

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