Climate Change and Overfishing Could Lead to More Toxic Seafood
Scientists continue to uncover more ways climate change poses a threat to our health, such as the spread of tropical diseases northward and the loss of crucial nutrients in crops. Now, researchers at Harvard have added another risk to that list: increased neurotoxins in seafood.
According to a new study, published in the journal Nature, overfishing and the rising temperature of the oceans are increasing the amount of methylmercury in commonly eaten fish such as tuna, cod and dogfish, despite decades of government regulations reducing mercury emissions from industry seeping into the water.
"You would expect that as mercury was reduced in seawater, then it would go down in all the fish," lead author Amina Schartup, who was a research associate at the Harvard School of Engineering and Applied Sciences, told NBC News. "But there was variability. We were trying to tease out the different factors contributing to those differences."
Methylmercury is a harmful toxin that can damage the heart and blood vessel system, reduce immune function, and could be particularly harmful to the nervous systems of pregnant women and their babies, the Centers for Disease Control and Prevention warns.
For the study, the researchers used 30 years of data from the Gulf of Maine to develop a food web model that shows how mercury levels in certain fish are affected by overfishing, warming waters and other environmental factors.
By the 1970s the Gulf of Maine had been overfished, particularly of herring, meaning that herring predators cod and dogfish were forced to find new prey. While cod switched to eating smaller fish, the dogfish started to eat squid and other high-mercury cephalopods.
The dogfish ended up with higher mercury levels, while mercury levels in cod dipped. After the fishery stocks rebounded, both fish returned to eating mostly herring. Cod saw a 23 percent mercury increase and the dogfish lowered their mercury levels after switching back. The model predicts that if the oceans were to warm by 1 degree Celsius over the 2000 temperature, mercury levels would jump by 32 percent in cod and 70 percent in dogfish, The Harvard Gazette reported.
The researchers then examined why mercury levels of Atlantic bluefin tuna have increased without any change in prey and amid decreasing mercury emissions from humans.
The model showed that in the 1990s, water temperatures in the Gulf of Maine temporary cooled, which corresponded with a decrease in mercury levels in the tuna. But climate change has steadily been warming the oceans and it's happening faster in the Gulf of Maine than most places, according to The Harvard Gazette. Following rising temperatures between 2012 and 2017, mercury levels in the tuna rose 3.5 percent per year, and could rise by 30 percent over 2015 levels by 2030.
The team identified two reasons for this.
One, tuna are higher on the food chain and use more energy than other fish, so they eat more prey that already contains mercury, Schartup said. Two, warmer waters mean that fish need to use more energy to swim and increase their calorie intake to do so. In total, mercury levels in tuna increased by 27 percent, the model suggested, due to the warming of their habitat.
But the researchers say they're not trying to scare people away from seafood.
"It's not that everyone should be terrified after reading our paper and stop eating seafood, which is very healthy, nutritious food," researcher Elsie Sunderland, a professor of environmental chemistry at Harvard University, told Al Jazeera. "We wanted to show people that [climate change] can have a direct impact on what you're eating today, that these things can affect your health ... not just things like severe weather and flooding and sea-level rise."
"If we do not act to lower greenhouse gas emissions, new fish species will enter the waters of at least 70 countries by 2100, challenging the regulatory framework for managing fishing rights" Read more: https://t.co/Ar7XBPik8Z— Our Children's Trust (@youthvgov) June 18, 2018
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By Matt Kasson, Brian Lovett and Carolee Bull
Home gardening is having a boom year across the U.S. Whether they're growing their own food in response to pandemic shortages or just looking for a diversion, numerous aspiring gardeners have constructed their first raised beds, and seeds are flying off suppliers' shelves. Now that gardens are largely planted, much of the work for the next several months revolves around keeping them healthy.
Start With Prevention<p>Just as preventive steps like maintaining a balanced diet help keep humans healthy, home growers can take many actions to help their gardens thrive.</p><p>One key step is assessing soil fertility – the ability of soil to sustain plant growth – which can vary widely depending on your location and soil type. Low soil fertility limits food production and predisposes plants to disease and pests. University extension <a href="https://soiltesting.wvu.edu/" target="_blank">soil testing labs</a> can help evaluate the quality of garden soil and identify nutrient deficiencies and acidic soils, often at no charge.</p>
Using weed barrier landscape cloth for planting rows and mulching between rows is an effective way to suppress weeds. Matt Kasson, CC BY-ND
Diagnosing Problems<p>Common plant pathogens include <a href="https://www.apsnet.org/edcenter/disandpath/viral/introduction/Pages/PlantViruses.aspx" target="_blank">viruses</a>, <a href="https://www.apsnet.org/edcenter/disandpath/prokaryote/intro/Pages/Bacteria.aspx" target="_blank">bacteria</a>, <a href="https://www.apsnet.org/edcenter/disandpath/nematode/intro/Pages/IntroNematodes.aspx" target="_blank">nematodes</a>, <a href="https://www.apsnet.org/edcenter/disandpath/oomycete/introduction/Pages/IntroOomycetes.aspx#:%7E:text=The%20oomycetes%2C%20also%20known%20as,foliar%20blights%20and%20downy%20mildews." target="_blank">oomycetes</a> and <a href="https://www.apsnet.org/edcenter/disandpath/fungalasco/intro/Pages/IntroFungi.aspx" target="_blank">fungi</a>. All of these microorganisms, especially at an early stage of infection, are too small to see. But when they proliferate, they cause changes in plants that we can recognize.</p><p>Unlike insects, which move around on six legs or on wings through the air, pathogens can move unseen and unchecked from leaf to leaf on the wind, through the soil or in droplets of water. Some microbes have even formed intimate relationships with insects and use them as vehicles to move from plant to plant, which makes these pathogens even more challenging to manage. Unfortunately, by the time some pathogens make their presence known, the damage is already done.</p><p>We recently conducted a <a href="https://twitter.com/kasson_wvu/status/1265989041725624323" target="_blank">Twitter poll</a> of gardeners nationwide to find out which culprits plagued their gardens. People named <a href="https://ento.psu.edu/extension/factsheets/aphids" target="_blank">aphids</a>, <a href="https://ento.psu.edu/extension/factsheets/squash-vine-borer" target="_blank">squash vine borers</a>, <a href="https://ento.psu.edu/extension/factsheets/squash-bug" target="_blank">squash bugs</a> and <a href="https://ento.psu.edu/extension/factsheets/flea-beetle" target="_blank">flea beetles</a> as the most problematic insect pests. Their most troublesome pathogens included <a href="https://extension.wvu.edu/lawn-gardening-pests/plant-disease/fruit-vegetable-diseases/powdery-mildew" target="_blank">powdery mildew</a>, <a href="https://plantpath.ifas.ufl.edu/rsol/Trainingmodules/BWTomato_Module.html" target="_blank">tomato bacterial wilt</a> and <a href="https://extension.wvu.edu/lawn-gardening-pests/plant-disease/fruit-vegetable-diseases/downy-mildew" target="_blank">cucurbit downy mildew</a>.</p><p>To manage such perennial challenges, the first step is to spend time closely looking at your plants. Do you notice any insects consistently hanging around, or molds colonizing leaves or other plant parts? How about symptoms such as blight, stunting, or leaves that are yellowing, browning or wilting?</p>
This white fungal growth is an early sign of powdery mildew on a leaf of susceptible summer squash. Matt Kasson, CC BY-ND
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By Emma Charlton
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Value of air conditioning imports in selected OECD countries. ScienceDirect
The ‘Golden Thread’<p>The <a href="https://www.endenergypoverty.org/reports" target="_blank">Global Commission to End Energy Poverty</a> calls access to energy the "golden thread" that weaves together economic growth, human development, and environmental sustainability. And one of the <a href="https://www.weforum.org/agenda/archive/sdg-07-affordable-and-clean-energy" target="_blank">United Nations' Sustainable Development Goals</a> is to ensure access to affordable, reliable, sustainable and modern energy for all by 2030.</p><p>Sustainability also has a large role to play in the future of energy and failing to embed green policies in COVID-19 stimulus packages and underinvesting in green infrastructure are current risks, according to the <a href="http://www3.weforum.org/docs/WEF_COVID_19_Risks_Outlook_Special_Edition_Pages.pdf" target="_blank">World Economic Forum</a>.</p><p>In its vision for a 'Great Reset' – building a better world after the pandemic – the Forum and the IMF jointly backed the <a href="https://www.weforum.org/agenda/2020/06/end-fossil-fuel-subsidies-economy-imf-georgieva-great-reset-climate/" target="_blank">transition to a green economy</a> and called for an end to fossil fuel subsidies.</p>
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