Mapping Plastic Pollution

Here, we analyzed and mapped data on plastic pollution and related mitigation efforts in areas adjacent to and inside of the San Diego MPAs in the Pacific Ocean.

We found two hotspots of plastic waste in the San Diego region:

(1) Areas visited by high numbers of tourists and special events

(2) River outlets from large rivers running through urban areas

Mitigation efforts in these areas could prevent further and significant dispersal of plastic into the environment, including in and around MPAs. We analyzed the effectiveness of some of these mitigation efforts, such as plastic bag bans, which we found reduced the amount of bags found over time. Other bans should show similar results in preempting plastic waste pollution.

• While ocean currents and gyres circulate ocean waters, they also draw in the plastic waste that travels towards coastal shorelines. Remote locations far from direct human influence are linked by plastic traveling from thousands of miles away.
• Here, we highlight pathways related to oceanic currents in which plastics can find their way to the San Diego County coastline.

While plastic pollution impairs marine ecosystems on various levels, special attention and care are needed to mitigate negative impacts in MPAs, which are especially sensitive and valuable ecosystems in the marine environment. San Diego county has 11 MPAs.

MPAs in San Diego are exposed to plastic waste pollution via multiple pathways. However, data on plastic waste is scarce, particularly regarding that near and in MPAs. Our plastic waste data consists of two coastal cleanup data portals which provide a snapshot of the plastic waste problem in San Diego County. In addition, data on riverine plastic fluxes, ecological and geological coastal features, and plastic pollution interventions were gathered for our analyses.

Plastic from rivers & the oceans can be captured by aquatic vegetation such as Kelp & Eelgrass.

Submerged aquatic vegetation (SAV) is often found close to the coast. Several SAV habitats are within the MPAs in San Diego where plastic can accumulate and harm the ecosystem.

Airbnb listings are indicators for tourist-dense areas in San Diego County. We see an increased amount of plastic waste in these areas, and surrounding areas from 2016-2020.

Tobacco products (cigarettes, cigars, packaging, and e-cigarettes) are the most common item found during a cleanup activity. The second and third most abundant items appear to be plastic food wrappers and plastic and foam fragments. Following these top three waste contestants, a lot of the remaining waste is due to food and beverage service items.

However, the good news is that plastic-related bans appear to be working. From the MarineDebris data, we see a visible decrease in the percent of waste containing plastic bags found through time!

• Cleanup activities decrease in areas close to MPAs (<1km) compared to those > 1-5 Km.

• Because tourism is the third most important driver of the economy in San Diego County, special attention should be given to reducing the impact of plastic in touristy areas.

• Since rivers are a major pathway of plastic entering the coast and ocean, future work should examine the effectiveness of river booms and improving upstream waste collection

• Submerged aquatic vegetation zones in & adjacent to MPAs in San Diego County are potential hotspots for riverine land-based and marine plastic waste accumulation.

• Plastic bag bans reduce the percent plastic bags found during cleanups in San Diego Co.

• We recommend regular monitoring and cleanup events near & inside of MPAs as our analyses demonstrated that cleanup efforts are significantly lower in & near MPAs (0-1 km) versus further away (>1-5 km). These plastic monitoring & cleanup activities would need to adhere to local regulations in each MPA to maintain low environmental impact.

• Ocean currents affect the distribution of plastic in the ocean and along the coastlines. We recommend further analyses and modeling ocean plastic flows into the MPAs and surrounding areas in San Diego County.

• Further analyses need to examine the flux of plastic from trash capture infrastructure (e.g. trash cans near shorelines and stormwater drainages) in order to more effectively prevent plastic from ending up in aquatic ecosystems.

• We suggest a standardized method for entering trash data from cleanup events, with critical information including the: 1) number of people participating in cleaning up the trash, & entering the data, 2) distance covered per person during a cleanup event, 3) estimated weight or volume of trash, 4) types & number of trash items collected, 5) date & time of the cleanup & 6) latitude and longitude of the cleanup site. Most importantly, the data should be easily accessible, with standardized column names & data formatting so that data can be combined across different cleanup entities & used for different purposes.