By Frank La Sorte and Kyle Horton
Millions of birds travel between their breeding and wintering grounds during spring and autumn migration, creating one of the greatest spectacles of the natural world. These journeys often span incredible distances. For example, the Blackpoll warbler, which weighs less than half an ounce, may travel up to 1,500 miles between its nesting grounds in Canada and its wintering grounds in the Caribbean and South America.
Blackpoll warbler. PJTurgeon / Wikipedia<p>We used this information to determine how the number of migratory bird species varies based on each city's level of <a href="https://www.britannica.com/science/light-pollution" target="_blank" rel="noopener noreferrer">light pollution</a> – brightening of the night sky caused by artificial light sources, such as buildings and streetlights. We also explored how species numbers vary based on the quantity of tree canopy cover and impervious surface, such as concrete and asphalt, within each city. Our findings show that cities can help migrating birds by planting more trees and reducing light pollution, especially during spring and autumn migration.</p>
Declining Bird Populations<p>Urban areas contain numerous dangers for migratory birds. The biggest threat is the risk of <a href="https://doi.org/10.1650/CONDOR-13-090.1" target="_blank">colliding with buildings or communication towers</a>. Many migratory bird populations have <a href="http://dx.doi.org/10.1126/science.aaw1313" target="_blank">declined over the past 50 years</a>, and it is possible that light pollution from cities is contributing to these losses.</p><p>Scientists widely agree that light pollution can <a href="https://doi.org/10.1073/pnas.1708574114" target="_blank">severely disorient migratory birds</a> and make it hard for them to navigate. Studies have shown that birds will cluster around brightly lit structures, much like insects flying around a porch light at night. Cities are the <a href="https://doi.org/10.1002/fee.2029" target="_blank" rel="noopener noreferrer">primary source of light pollution for migratory birds</a>, and these species tend to be more abundant within cities <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13792" target="_blank" rel="noopener noreferrer">during migration</a>, especially in <a href="https://doi.org/10.1016/j.landurbplan.2020.103892" target="_blank" rel="noopener noreferrer">city parks</a>.</p>
Composite image of the continental U.S. at night from satellite photos. NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA's Goddard Space Flight Center
The Power of Citizen Science<p>It's not easy to observe and document bird migration, especially for species that migrate at night. The main challenge is that many of these species are very small, which limits scientists' ability to use electronic tracking devices.</p><p>With the growth of the internet and other information technologies, new data resources are becoming available that are making it possible to overcome some of these challenges. <a href="https://doi.org/10.1038/d41586-018-07106-5" target="_blank">Citizen science initiatives</a> in which volunteers use online portals to enter their observations of the natural world have become an important resource for researchers.</p><p>One such initiative, <a href="https://ebird.org/home" target="_blank" rel="noopener noreferrer">eBird</a>, allows bird-watchers around the globe to share their observations from any location and time. This has produced one of the <a href="https://doi.org/10.1111/ecog.04632" target="_blank" rel="noopener noreferrer">largest ecological citizen-science databases in the world</a>. To date, eBird contains over 922 million bird observations compiled by over 617,000 participants.</p>
Light Pollution Both Attracts and Repels Migratory Birds<p>Migratory bird species have evolved to use certain migration routes and types of habitat, such as forests, grasslands or marshes. While humans may enjoy seeing migratory birds appear in urban areas, it's generally not good for bird populations. In addition to the many hazards that exist in urban areas, cities typically lack the food resources and cover that birds need during migration or when raising their young. As scientists, we're concerned when we see evidence that migratory birds are being drawn away from their traditional migration routes and natural habitats.</p><p>Through our analysis of eBird data, we found that cities contained the greatest numbers of migratory bird species during spring and autumn migration. Higher levels of light pollution were associated with more species during migration – evidence that light pollution attracts migratory birds to cities across the U.S. This is cause for concern, as it shows that the influence of light pollution on migratory behavior is strong enough to increase the number of species that would normally be found in urban areas.</p><p>In contrast, we found that higher levels of light pollution were associated with fewer migratory bird species during the summer and winter. This is likely due to the scarcity of suitable habitat in cities, such as large forest patches, in combination with the adverse affects of light pollution on bird behavior and health. In addition, during these seasons, migratory birds are active only during the day and their populations are largely stationary, creating few opportunities for light pollution to attract them to urban areas.</p>
Trees and Pavement<p>We found that tree canopy cover was associated with more migratory bird species during spring migration and the summer. Trees provide important habitat for migratory birds during migration and the breeding season, so the presence of trees can have a strong effect on the number of migratory bird species that occur in cities.</p><p>Finally, we found that higher levels of impervious surface were associated with more migratory bird species during the winter. This result is somewhat surprising. It could be a product of the <a href="https://www.epa.gov/heatislands" target="_blank">urban heat island effect</a> – the fact that structures and paved surfaces in cities absorb and reemit more of the sun's heat than natural surfaces. Replacing vegetation with buildings, roads and parking lots can therefore make cities significantly warmer than surrounding lands. This effect could reduce cold stress on birds and increase food resources, such as insect populations, during the winter.</p><p>Our research adds to our understanding of how conditions in cities can both help and hurt migratory bird populations. We hope that our findings will inform urban planning initiatives and strategies to reduce the harmful effects of cities on migratory birds through such measures as <a href="https://www.arborday.org/programs/treecityusa/index.cfm" target="_blank" rel="noopener noreferrer">planting more trees</a> and initiating <a href="https://aeroecolab.com/uslights" target="_blank" rel="noopener noreferrer">lights-out programs</a>. Efforts to make it easier for migratory birds to complete their incredible journeys will help maintain their populations into the future.</p><p><em><span style="background-color: initial;"><a href="https://theconversation.com/profiles/frank-la-sorte-1191494" target="_blank">Frank La Sorte</a> is a r</span>esearch associate at the </em><em>Cornell Lab of Ornithology, Cornell University. <a href="https://theconversation.com/profiles/kyle-horton-1191498" target="_blank">Kyle Horton</a> is an assistant professor of Fish, Wildlife, and Conservation Biology at the Colorado State University.</em></p><p><em></em><em>Disclosure statement: Frank La Sorte receives funding from The Wolf Creek Charitable Foundation and the National Science Foundation (DBI-1939187). K</em><em>yle Horton does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</em></p><p><em>Reposted with permission from <a href="https://theconversation.com/cities-can-help-migrating-birds-on-their-way-by-planting-more-trees-and-turning-lights-off-at-night-152573" target="_blank">The Conversation</a>. </em></p>
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Light pollution is increasing near coral reefs as coastal developments expand. Some bungalows are even built above the reef with clear floors, so that tourists can watch the fish at night. But that means the fish can see the light from the bungalows, too.
According to the UN Environment Program, up to 5 trillion single-use plastic bags are used globally each year, and because of the material they're made from, most municipal recycling centers don't accept them (more on this below).
The most sustainable option is to skip the bag altogether. You can also make your own reusable produce bags out of old T-shirts. But if you'd rather purchase them new, here are our recommendations for the best reusable produce bags on the market today.
Eco Joy<p>If you're making the switch to more sustainable shopping bags and want a variety of products to use, the <a href="https://www.amazon.com/Reusable-Sandwich-Biodegradable-Eco-Drawstring/dp/B003PK4W3I/ref=sr_1_36?crid=3TDUCB8ZOM7WI&dchild=1&keywords=produce+bags+grocery+reusable&qid=1613484643&sprefix=produce+bags%2Caps%2C189&sr=8-36" target="_blank">Eco Joy Cotton Reusable Produce Bags</a> set is a great place to start. The set comes with three mesh drawstring bags, three muslin drawstring bags, a large mesh tote and a zippered sandwich-size pouch.</p><p>Each product is made with organic, non-GMO cotton that's ethically sourced in accordance with Worldwide Responsible Accredited Production (WRAP) standards. The cotton comes from India and Turkey, and the bags are hand-assembled in Canada by the owner of Eco Joy, so you can feel good about supporting a small business while reducing your environmental impact.</p><p><strong>Customer rating:</strong> 4.7 out of 5 stars with over 300 Amazon reviews</p><p><strong>Why buy: </strong>Zero-waste; Handmade in Canada; WRAP compliant; Machine washable</p>
Organic Cotton Mart<p>Some shoppers prefer to use mesh bags when shopping for fruits and veggies. We recommend checking out <a href="https://www.amazon.com/Best-Reusable-Produce-Organic-Cotton/dp/B07CK2TJKL/ref=sr_1_16?crid=10A7NM0LQ0B7E&dchild=1&keywords=mesh+produce+bags&qid=1613483897&s=home-garden&sprefix=mesh+pro%2Cgarden%2C162&sr=1-16" target="_blank">Organic Cotton Mart's Reusable Cotton Mesh Produce Bags</a> if you're in this camp, as they're made with Global Organic Textile Standard (GOTS) certified cotton.</p> <p>Mesh reusable produce bags can make the checkout process easier than muslin bags since you can see what's inside them without having to open them up. Plus, the tare weight (i.e., the weight of the empty bag that should be subtracted from the total weight of your produce to make sure you don't pay extra for using your bag) is printed right on the label of Organic Cotton Mart's bags, making everything that much more convenient.</p> <p><strong>Customer rating:</strong> 4.6 out of 5 stars with nearly 1,000 Amazon reviews</p><strong>Why buy:</strong> GOTS certified; Machine washable; Biodegradable
Simple Ecology<p>On the other hand, if you just want to purchase muslin bags, we like <a href="https://www.amazon.com/Simple-Ecology-Reusable-Organic-Shopping/dp/B004UJ0U0C" target="_blank">Simple Ecology's Reusable Produce Bags</a>, which are also made with GOTS-certified organic cotton. Simple Ecology also has a <a href="https://www.amazon.com/dp/B01N6AUMBG/ref=sspa_dk_detail_2?psc=1&pd_rd_i=B01N6AUMBG&pd_rd_w=MA3ZS&pf_rd_p=cbc856ed-1371-4f23-b89d-d3fb30edf66d&pd_rd_wg=hVunQ&pf_rd_r=G6RTQ1Z5DKEY325MAJZ9&pd_rd_r=5d298b3a-1be7-4ebd-a9e1-d5d672a40497&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExMzc4RVAxWjNLOTdCJmVuY3J5cHRlZElkPUEwNTc0NTAwMzBDMjFYOVJPTUpWSCZlbmNyeXB0ZWRBZElkPUEwNjYyOTM4M0s4Vk81SVBPS1NFSyZ3aWRnZXROYW1lPXNwX2RldGFpbF90aGVtYXRpYyZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=" target="_blank">starter kit</a> that comes with several reusable grocery bags if you're looking for more variety.</p> <p>The benefit of using muslin reusable produce bags is that, unlike mesh, there are no holes for small items to slip through. This means that in addition to larger produce, you can use them to purchase bulk foods like lentils, beans and rice — or even powders like flour or spices — without worrying about anything leaking. They're also best for keeping leafy greens fresh.</p> <p><strong>Customer rating:</strong> 4.7 out of 5 stars with nearly 1,500 Amazon reviews</p><strong>Why buy:</strong> GOTS certified; Machine washable; Biodegradable; Sustainable Forestry Initiative (SFI) certified packaging when purchased from manufacturer
ECOBAGS<p>Whether you're buying bread, fresh flowers, produce or all of the above, the <a href="https://www.amazon.com/ECOBAGS-Market-Collection-Reusable-Natural/dp/B08KFGPGN5" target="_blank" rel="noopener noreferrer">ECOBAGS Market Collection Reusable Bag Set</a> is ideal for <a href="https://www.ecowatch.com/farmers-markets-coronavirus-safety-2645581711.html" target="_self">farmers market</a> shopping or large grocery hauls. The netted bags are durable, flexible, and pack down small so they're easy to keep in your car or purse.</p> <p>ECOBAGS is a woman-owned certified B Corp, which means it uses sound social and environmental practices. These bags come in packs of three or five and have a few different handle lengths and color options, but they're all made with GOTS-certified organic cotton.</p> <p><strong>Customer rating: </strong>Not applicable</p><p><strong>Why buy:</strong> GOTS certified; Machine washable; Biodegradable; Certified B Corp; SA8000 certified for the protection of basic human rights of workers</p>
An estimated 600 million birds are killed every year from collisions with some of the country's largest skyscrapers, according to research from the Cornell Lab of Ornithology. Particularly deadly are those tall buildings found in three cities in particular.
Composite image of continental U.S. at night, 2016.
A chestnut-sided warbler
Patricia Leonard, Cornell Lab of Ornithology
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What are the most dangerous U.S. cities for migratory birds?
That's the question answered by a new study published last week in Frontiers in Ecology and the Environment, which looked at the problem of light pollution. Seventy percent of bird species present in the U.S. are migratory, and more than 80 percent of those species migrate at night. The increasing light pollution of cities attracts the avian travelers, who then crash into buildings. Building collisions kill an estimated 600 million birds in the U.S. every year, according to the Cornell Lab of Ornithology, which led the study.
The researchers created two lists for the cities that pose the greatest risk to birds during both the spring and fall migratory season, based on both geography and light pollution.
By Dipika Kadaba
The amount of artificial lighting is steadily increasing every year around the planet. It's a cause for celebration in remote villages in Africa and the Indian sub-continent that recently gained access to electricity for the first time, but it is also harming the health and well-being of residents of megacities elsewhere that continue to get bigger and brighter every year.
Health impacts of this artificial illumination after daylight hours range from depression to cancer, including a range of sleep disorders.
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NASA scientists created the most complete map of Earth at night to date—showing humans in all of their electric glory. But, while the photos are magical, they also show human's extreme effect on the planet.