University of Florida
The BP Deepwater Horizon oil spill temporarily worsened existing manmade problems in Louisiana's salt marshes such as erosion, but there may be cause for optimism, according to a new study.
A study appearing online Monday in the Proceedings of the National Academy of Sciences found the 2010 spill killed off salt marsh plants 15 to 30 feet from the shoreline and this plant die off resulted in a more-than-doubled rate of erosion along the marsh edge and subsequent permanent marsh habitat loss. Vegetation farther from shore was relatively untouched by the incoming oil.
"Louisiana is already losing about a football field worth of wetlands every hour, and that was before the spill," said Brian Silliman, a University of Florida biologist and lead author of the study. "When grasses die from heavy oiling, their roots, that hold the marsh sediment together, also often die. By killing grasses on the marsh shoreline, the spill pushed erosion rates on the marsh edge to more than double what they were before. Because Louisiana was already experiencing significant erosive marsh loss due to the channelization of the Mississippi, this is a big example of how multiple human stressors can have additive effects."
Marshes are the life's blood of coastal Louisiana because they act as critical nurseries for the shrimp, oysters and fish produced in these waters while helping to sequester significant amounts of carbon. They also protect coastlines from flooding and guard estuarine waters from nutrient pollution.
But the marshes have been suffering for decades as a result of the channelization of the Mississippi River, which has starved them from needed sediments to deter erosion.
Then came the oil spill.
Researchers observed minimal oil on the surfaces of grasses located more than 45 feet from the shoreline, indicating that significant amounts of oil did not move into interior marshes.
Instead, the researchers found that the tall grasses along the marsh edge acted as wall-like trap to incoming oil slicks, concentrating oil on the marsh edge. This concentration of oil on the shoreline protected interior marshes from oiling but worsened already extreme erosion on the shoreline. As oiled plants died, their roots that hold tight to the sediment perished as well. Already eroding sediment was now exposed to wave action without the effect of the gripping plant roots.
The result: elevated erosion rates for 1.5 years that averaged more than 10 feet of shoreline loss per year—double the natural rate for this area.
The encouraging results, Silliman said, included significant declines in the oil concentration on the marsh surface over 1.5 years and that unaffected, healthy marsh plants in the marsh interior quickly grew back into marsh die-off areas that had not yet been lost due to heightened erosion.
When the new marsh plant growth grew into the erosive edge of the marsh, Silliman said, the recolonization of the area by the gripping plant roots shut down the oil-elevated erosion rates and returned them to those seen at marsh sites where oil coverage did not occur.
The researchers also found that polyaromatic hydrocarbons, or PAHs, a carcinogenic byproduct of oil, was 100 percent greater at the Barateria Bay testing site than in reference marshes. This finding provides chemical evidence to support their visual observations that marshes in the affected areas were laden with oil while those in reference areas did not receive significant oiling.
By adding Biochar, a charcoal-based substance, to marshlands, Silliman's team is also using new bioremediation tactics to try to break down PAHs into organic material. If this method is successful, he said, it could be used to supplement naturally occurring microbes in the marsh mud that already oxidize the oil carcinogen. The team is soon to publish those findings.
"This is a new idea applied toward cleaning up PAHs," said UF chemistry professor Andrew R. Zimmerman, a co-author on the paper. "It's possible there's a bunch lurking at the bottom of the bay."
Visit EcoWatch's GULF OIL SPILL page for more related news on this topic.
"Now that we are spending more time at home, we are noticing the large number of delivery vans and lorries driving through cities," said Netherlands environment minister Stientje van Veldhoven, announcing plans to ban all but zero-emission deliveries in 14 cities.
"The agreements we are setting down will ensure that it will be a matter of course that within a few years, supermarket shelves will be stocked, waste will be collected, and packages will arrive on time, yet without any exhaust fumes and CO2 emissions," she added.
She expects 30 cities to announce zero emission urban logistics by this summer. City councils must give four years' notice before imposing bans as part of government plans for emission-free road traffic by 2050. The city bans aim to save 1 megaton of CO2 each year by 2030.
Help to Change
To encourage transport organizations to go carbon-free, the government is offering grants of more than US$5,900 to help businesses buy or lease electric vehicles. There will be additional measures to help small businesses make the change.
The Netherlands claims it is the first country in the world to give its cities the freedom to implement zero-emission zones. Amsterdam, Rotterdam and Utrecht already have "milieuzones" where some types of vehicles are banned.
Tilburg, one of the first wave of cities imposing the Dutch ban, will not allow fossil-fuelled vehicles on streets within its outer ring road and plans to roll out a network of city-wide electric vehicle charging stations before the ban comes into effect in 2025.
"Such initiatives are imperative to improve air quality. The transport of the future must be emission-free, sustainable, and clean," said Tilburg city alderman Oscar Dusschooten.
Europe Takes Action
Research by Renault shows that many other European cities are heading in the same direction as the Netherlands, starting with Low Emission Zones of which Germany's "Umweltzone" were pioneers. More than 100 communes in Italy have introduced "Zonas a traffico limitato."
Madrid's "zona de baja emisión" bans diesel vehicles built before 2006 and petrol vehicles from before 2000 from central areas of the city. Barcelona has similar restrictions and the law will require all towns of more than 50,000 inhabitants to follow suit.
Perhaps the most stringent restrictions apply in London's Ultra Low Emission Zone (ULEZ), which charges trucks and large vehicles up to US$137 a day to enter the central area if they do not comply with Euro 6 emissions standards. From October, the ULEZ is being expanded.
Cities are responsible for around 75% of CO2 emissions from global final energy use, according to the green thinktank REN21 - and much of these come from transport. Globally, transport accounts for 24% of world CO2 emissions.
The Rise of Online Shopping
Part of the reason for traffic in urban areas is the increase in delivery vehicles, as online shopping continues to grow. Retailer ecommerce sales are expected to pass $5billion in 2022, according to eMarketer.
The World Economic Forum's report The Future of the Last-Mile Ecosystem, published in January 2020, estimates that e-commerce will increase the number of delivery vehicles on the roads of the world's 100 largest cities by 36% by 2030.
If all those vehicles burn fossil fuels, the report says emissions will increase by 32%. But switching to all-electric delivery vehicles would cut emissions by 30% from current levels as well as reducing costs by 25%, the report says.
Other solutions explored in the report include introducing goods trams to handle deliveries alongside their passenger-carrying counterparts and increased use of parcel lockers to reduce the number of doorstep deliveries.
Reposted with permission from the World Economic Forum.