subtropical

Mangrove Trees And Climate Change | Earth Wise

July 7, 2020 By EarthWise Leave a Comment

Mangrove trees are small trees that grow in coastal saline or brackish water at tropical and subtropical latitudes. Many mangrove trees can be identified by their dense tangle of prop roots. These roots make the trees appear as if they are standing on stilts above the water. The tangle of roots allows mangrove trees to handle the daily rise and fall of tides and to slow the movement of tidal waters.

Mangrove forests provide many ecosystem services, including stabilizing the coastline by reducing erosion from storm surges, waves, and tides. The intricate root system of mangrove trees are attractive to fish and other species seeking food and shelter from predators. Mangrove forests also store large amounts of carbon.

But according to a new study recently published in the journal Science, mangrove trees won’t survive sea level rise by 2050 if greenhouse gas emissions aren’t reduced.

Using sediment data from 78 locations over the last 10,000 years, an international team of scientists led by Macquarie University in Australia estimated the chances of mangrove trees survival based on the projected rates of future sea-level rise.

When sea level rise rates exceeded 6 millimeters per year, which is similar to estimates under high-emissions scenarios for 2050, researchers found that mangrove trees were unlikely to keep pace with the rising water levels. But when the annual increase was 5 millimeters or less – which is the projected low-emissions scenario this century – mangrove trees are much more likely to survive.

These findings underscore the importance of reducing greenhouse gas emissions to mitigate rapid sea level rise. The future of mangrove trees may depend on it.

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Mangrove trees won’t survive sea-level rise by 2050 if emissions aren’t cut

Photo, posted December 17, 2012, courtesy of Edward Stojakovic via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Fighting Malaria With Gene-Drive Technology | Earth Wise

June 8, 2020 By EarthWise Leave a Comment

Malaria continues to be a major health hazard throughout the tropical and subtropical regions of the world. There were 228 million cases of malaria in 2018 and over 400,000 deaths.

Malaria is a mosquito-borne infectious disease spread by 40 of the world’s 3,500 mosquito species. So, efforts to control mosquito populations are the primary strategy to eradicate malaria.

A team led by Imperial College London has created a genetic modification that distorts the sex ratio of a population of Anopheles gambiae mosquitoes using “gene drive” technology. The modification works by using a DNA-cutting enzyme to destroy the X chromosome during the production of sperm, which leads to predominantly male offspring, since females require two X chromosomes. The modification is coupled to a gene drive to allow it to spread through a population in a very effective way. A gene drive is a genetic engineering technology that propagates a particular modification by assuring that a specific form of a gene (or allele) will be transmitted with far more than the natural 50% probability.

The result of this is that mosquitoes produce more male offspring, eventually leading to no females being born and a total collapse in the population. The mosquitoes studied are the main malaria vector in sub-Saharan Africa. The hope is that mosquitoes carrying a sex-distorter gene drive would be released in the future, spreading the male bias with local malaria-carrying populations and causing them to collapse. Only female mosquitoes bite and take blood meals. If the gene drive technology works in the field, it could be a game-changer in the fight to eliminate malaria.

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Malaria mosquitoes eliminated in lab by creating all-male populations

Photo, posted June 20, 2014, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Mistaking Plastic For Food

September 27, 2019 By EarthWise Leave a Comment

Green sea turtles are one of the world’s largest species of turtle, with some measuring close to four feet long and weighing up to nearly 300 pounds. Their range extends throughout tropical and subtropical seas around the world, with the largest nesting populations found in Costa Rica and Australia.

Green sea turtles get their name from the green layer of fat under their shell, as opposed to their shell itself, which can be brown, green, yellow, and/or black. Scientists believe the green coloring of their fat is a result of their diet. Unlike most other sea turtles, green sea turtles eat marine plants such as seaweed and seagrass.

But new research suggests that green sea turtles are also more likely to swallow plastic because it resembles their natural diet. The scientists from the University of Exeter and the Society for the Protection of Turtles who examined green sea turtles that washed up on beaches in Cyprus found they favored narrow lengths of plastic in natural colors (like green and black) as opposed to debris of other shapes and colors.

Researchers were able to examine the full gastrointestinal tract of 19 green sea turtles. They found pieces of plastic inside every one of them, with the number of pieces ranging from three to 183. Smaller turtles tended to contain more plastic, possibly because they are less experienced or because diet choices change with age and size.

Previous research has suggested that leatherback sea turtles also eat plastic that resembles their food: jellyfish.

Researchers hope these findings will help motivate us to continue to work on reducing our overall plastic consumption and pollution.

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Green turtles eat plastic that looks like their food

Photo, posted September, 2007, courtesy of Brock Roseberry via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Refugee Corals

August 30, 2019 By EarthWise Leave a Comment

As climate change warms the ocean, subtropical environments are becoming more favorable for corals than the equatorial waters where they traditionally thrived. As a result, drifting coral larvae are settling and growing in new regions.

According to new research in the journal Marine Ecology Progress Series, the number of young corals on tropical reefs has declined by 85% over the past 40 years. At the same time, the numbers on subtropical reefs has doubled.

Only certain types of coral can reach these new subtropical locations. That depends on how far the microscopic larvae can swim and drift on currents before they exhaust their limited fat stores. Thus, the reef ecosystems that develop have new blends of species that have previously never coexisted. It is not clear how long it will take for the new systems to reach equilibrium.

Coral reefs are complicated systems that depend on the interplay between species to enable their healthy functioning. Apart from the corals themselves, there are the coraline algae that symbiotically coexist with them. How all of this will play out in these evolving ecosystems is unknown.

In the meantime, the research has found that these refugee corals are settling at latitudes up to 35 degrees both north and south of the equator. It is no longer so clear what constitute native species in the reefs. It remains to be seen whether new reefs in subtropical oceans can support the incredible biodiversity seen in tropical reefs. But ultimately, these changing ecosystems could potentially bring new resources and opportunities, such as fishing and tourism, to places where they never existed before.

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Coral Reefs Shifting Away from Equatorial Waters

Photo, posted March 22, 2011, courtesy of Simone Lovati via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.