Dear EarthTalk: How has the huge footprint of humanity forced other animal and plant species to evolve differently than they might otherwise have without people around? ~ Lois V., New York, NY
Humans have profoundly altered the planet, driving plants and animals to adapt in ways they never would have without our impact. Through activities like habitat destruction, pollution, climate change, hunting and introducing invasive species, humans have significantly accelerated evolutionary changes, transforming ecosystems in dramatic and often unpredictable ways.
One example is the rise of tuskless elephants. Decades of ivory poaching have created intense pressure on African elephants. In regions of heavy poaching, up to half of female elephants are now tuskless, an adaptation showing how humans can profoundly alter the genetic makeup of another animal population.
Urban environments have also become hotspots for what some researchers consider accelerated evolution. During the Industrial Revolution, peppered moths in England evolved darker colors to blend into soot-covered trees. Today, insects and city-dwelling birds are similarly adapting to human-made conditions. Pigeons have modified their eating habits to thrive on discarded food, and some mosquito species have adapted to reproduce in tiny water collections present in city environments. These alterations illustrate the adaptability of species adjusting to environments changed by humans.
Chemical resistance is another area where human influence is clear. The widespread use of pesticides and antibiotics has driven the evolution of resistant pests and bacteria. Farmers battle “superweeds” that can survive herbicides, and healthcare providers face rising concerns over antibiotic-resistant bacteria.
Climate change has further expedited evolutionary shifts. Animals are altering their migration patterns and breeding seasons to adapt to warmer temperatures. Birds like the great tit in Europe are laying eggs earlier in the spring to align with the availability of insects. Similarly, marine species are moving to cooler waters. This disrupts ecosystems and fisheries
These adaptations showcase the nature’s incredible resilience, despite some notable drawbacks. Rapid evolution can lead to reduced biodiversity, as species unable to adapt face extinction. Ecosystem imbalances arise as invasive species prevail, pushing out native organisms. According to the National Wildlife Federation, human activities are driving an unprecedented rate of evolutionary change. To help, choose sustainably sourced products, reduce waste, and support conservation efforts to protect habitats and species. Advocacy for policies that address climate change and pollution is also key.
MORE INFORMATION: www.scientificamerican.com/article/humans-are-driving-a-new-kind-of-evolution-in-animals/
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Dear EarthTalk: What are so-called “green corridors” in cities and how do they help mitigate climate change? ~ Peter Q, Boston, MA
Green corridors, or ecological corridors, are strips of vegetation and natural landscape dispersed throughout a city. From simple, street-lined rows of trees to interconnected networks of parks and pathways, these developments provide a flexible, natural solution for the climate effects of urbanization.
One of the most pressing environmental hazards cities face today is the urban heat island effect. Large buildings, expansive roads and other man-made infrastructures absorb more heat than surrounding rural areas, leading to significantly higher temperature levels. When combined with global warming, these uncomfortable living conditions can be very detrimental for urban residents. Local air quality also deteriorates from industrial and transportation pollution. With an expected 68 percent of world population in cities by 2050, according to the U.N., the health situation in urban environments will only grow worse.
Green corridors offer a promising start to mitigating these urban issues, allowing cities to naturally lower temperatures through evapotranspiration, a plant process that releases water vapor to cool the surrounding air. Increased vegetation will also allow more hazardous particulate matter (PM2.5) and carbon dioxide (CO2) to be absorbed, reducing greenhouse gas concentration and improving air quality.
Columbia’s second-largest city, Medellín, launched a green corridor initiative in 2016. Since then, environmental planners there added rows of vegetation along the most polluted avenues, maximizing the amount of CO2 intake from their $16.8 million investment. Maurício Correa, a researcher studying environmental engineering at a Colombian University, found that the 8,800 trees planted became effective “green barriers” against particulate matter and reduced average city temperature by two degrees Celsius.
Fighting climate change isn’t the only thing green corridors can do. Historically, wildlife has rarely been welcomed into urban life, experiencing drastic changes in the ecosystem. However, nature-based infrastructure can promote biodiversity and provide animal species with a safe habitat. Green corridors are indeed multi-purpose and flexible. To maximize the limited space in busy cities, green corridors can function as recreational centers, city facilities and much more—all while mitigating climate change.
Green corridors can be an effective solution for any city anywhere. In New York, the Manhattan Waterfront Greenway consists of almost 32 miles of bike path lined with various plant species. Urban “Nature Ways” in Singapore mimic the natural rainforests by incorporating trees with canopies stretching across the roads.
MORE INFORMATION: bbc.com/future/article/20230922-how-medellin-is-beating-the-heat-with-green-corridors
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Dear EarthTalk: Why is the Great Salt Lake shrinking so much and can it be saved? ~ E.T., via email
Utah’s Great Salt Lake is the largest saltwater lake in the Western Hemisphere. It is a remnant of Lake Bonneville, which dried up 14,000 years ago due to extreme drought. It contributes $1.9 billion annually to Utah’s economy and provides 7,700 jobs. Over 10 million birds rely on this lake for their survival.
Apart from natural fluctuations, the Great Salt Lake’s water level has dropped continuously since 1870, mainly due to the desiccation of the lake in the diversion of upstream water. The Great Salt Lake gets most of its water from the Bear, Weber and Jordan rivers, but now a significant portion of water is being diverted for agricultural and industrial use. Climate change and increase in temperature are also contributing to the Great Salt Lake’s desiccation. Due to temperature increases, the rate of evaporation has also increased, impacting the salinity of the lake. Agriculture dominates water use by 74 percent, nine percent by mineral extraction, nine percent by industrial use and eight percent by evaporation.
“The lake has a lot of social and economic relevance for the region and Utah,” says Siiri Bigalke, a climate scientist at Portland State University who has studied recent volume levels of the Great Salt Lake. Indeed, the cost of the Great Salt Lake drying—including loss of mineral extraction, landscape mitigation costs, the loss of lake recreation and economic value, the loss of brine shrimp, health costs, and impacts to ski resorts—could total as much as $2.17 billion per year. The decline in Great Salt Lake water levels could kill some 6,500 jobs, most of which stem from a loss of mineral extraction output. Researchers say the tax rate in Utah would have to increase by more than 50 percent to make up for these potential losses.
The desiccation of the Great Salt Lake will lead to air and water pollution, a decline in agricultural productivity, loss of industry, and economic devastation. Even if the lake is not completely lost, the shrinkage can expose lakebed sediments containing heavy metals and organic pollutants which could significantly deteriorate air quality.
To save the lake, a minimum streamflow of 2.5 million acre-feet per year must be maintained. Ensuring that river flow remains at or above this threshold is essential for stabilizing the lake’s water levels. Water flow to upstream farms should be limited. Local governments should coordinate with state and federal programs to expand water conservation awareness. You can get involved by creating and sharing media on this issue to raise awareness. Additionally outdoor vegetation should be converted to drought tolerant to conserve water.
MORE INFORMATION: https://ballardbrief.byu.edu/issue-briefs/the-aridification-of-the-great-salt-lake
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