You’ve probably seen the images of dolphins caught in abandoned mono-filament fishing nets, or of vast areas of plastic trash floating in remote waters of the Pacific, or of sea turtles consuming plastic bags that look remarkably like one of their favorite foods: jellyfish.Or perhaps, after a rainstorm, you’ve walked on a beach that resembled a landfill. Some 20 million tons of plastic pollution enters the oceans each year, and it’s devastating the marine environment.Plastic litter is also costly. On the West Coast alone, according to a recent EPA study, the cost of cleaning up marine litter comes to more than $13 per person per year. And because plastic typically does not degrade in the ocean, today’s pollution will be a problem for many generations to come.Thanks to state and federal environmental requirements, the Los Angeles region has installed screens on more than 50,000 storm water basins, as well as inserts that keep all but the smallest plastic pollution out of local rivers, beaches and bays. Additionally, bans on single-use plastic bags in a number of jurisdictions have reduced plastic bag use by tens of millions of bags annually. And some coastal areas have banned single-use foam food packaging. All of these measures have meant less plastic ending up in the ocean.But we need far more comprehensive policies. A recent UCLA study analyzed dozens of treaties, programs and policies in place around the world and found all of them to be severely lacking.Overall, the well-intentioned international agreements impose vague or voluntary standards, require little to no monitoring, are severely underfunded and are difficult to enforce. In fact, the UCLA researchers concluded that there was essentially no recourse under international law to address most plastic marine litter on the high seas.Even the most effective of the current treaties, the International Convention for the Prevention of Pollution from Ships, has huge loopholes. For example, the treaty exempts accidental loss or disposal of plastic resulting from ship or equipment damage, and it leaves enforcement and penalty decisions up to often-reluctant states.To achieve the dramatic reductions necessary to stem the plastic marine litter crisis, we need a comprehensive solution akin to the Montreal Protocol, an international treaty that has dramatically reduced the global use of ozone-depleting chlorofluorocarbons. An effective treaty would include strict monitoring requirements, third-party compliance assessment, funding mechanisms and easily enforceable requirements with substantial penalties.One big problem is that international environmental treaties can take a decade or more to negotiate. In the interim, concerned countries must also pursue regional, national and local policies and programs to address plastic marine litter.Potential actions could include the creation of an “ocean-friendly” product certification program; regional and national bans on the most common and damaging types of plastic litter; the expansion of programs that provide economic incentives for manufacturers to manage plastic waste sustainably; the creation and implementation of certification and tracking programs for fishing and aquaculture operations; and the establishment of funding sources for marine litter remediation through product redemption fees and shipping container fees at ports.No individual action will solve the plastic marine litter crisis, but swift implementation of these policies could have a huge positive effect in reducing a crucial environmental problem. Mark Gold is associate director of the UCLA Institute of the Environment and Sustainability. Cara Horowitz is executive director of the Emmett Center on Climate Change and the Environment at UCLA Law School.