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Since these dense lower waters don't mixwith the warmer freshwater above,it can take four months for tropical storms to fully circulate oxygenated water back into the gulf.This dead zone currently costs U.S. seafood and tourism industries as much as $82 million a year,and that cost will only increase as the dead zone gets bigger.On average the gulf dead zone is roughly 15,000 square kilometers,but in 2019 it grew to over 22,000 square kilometers approximately the size of New Jersey.

Human activity is similarly responsible for growing dead zones around the world.So what can be done?In the short term, countries can set tighter regulations on industrial run-off,and ban the dumping of untreated sewage into ocean waters.On farms, we can plant buffer zones composed of trees and shrubs to absorb runoff.However, long term solutions will require radical changes to the way we grow food.

Farmers are currently incentivized to use techniques that reduce the health of the soil and rely heavily on nitrogen-rich fertilizers.But there would be less need for these chemicals if we restore the soil natural nutrients by planting diverse crops that manage soil erosion and fertility.Hopefully we can make these fundamental changes soon.Because if we don't the future of our marine ecosystems may be dead in the water.

states, including America top agricultural producers,are connected to the Mississippi River Basin,and all of their runoff drains into the Gulf of Mexico.Farmers apply most of this fertilizer during the spring planting season,so the nutrient flood occurs shortly after.In the Gulf,decomposing algae sinks into the band of cold saltwater near the seafloor.

But human activity has made eutrophication a regular and widespread occurrence.Nutrient-rich waste from our sewage systems and industrial processes often end up in lakes, estuaries and coastal waters.And the Gulf of Mexico is one of the largest dumping zones on earth for one particular pollutant: fertilizer.American agriculture relies heavily on nitrogen and phosphate-based fertilizers.

These light-deprived plants die off and decompose in a process which uses up the water already depleted oxygen supply.Over time, this can reduce the oxygen content to less than 2 milligrams of oxygen per liter,creating an uninhabitable dead zone.There are rare bodies of water that rely on natural eutrophication.Regions like the Bay of Bengal are full of bottom-dwelling marine life that has adapted to low-oxygen conditions.

While such resources are typically in short supply,sometimes the surrounding watershed can flood coastal waters with these nutrients.For example, a large rainstorm might wash nutrient-rich sediment from a forest into a lake.These additional resources lead to a massive increase in algae growth known as eutrophication.But rather than providing more food and oxygen,this surge of growth has deadly consequences.As more algae grows on the surface, it blocks sunlight to the plants below.

Clouds of algae streak the surface of deep waters,and in shallower regions, large seaweeds and seagrass cover the ground.Not only do these organisms form the foundation of local food chains,their photosynthesis provides the oxygen necessary for aquatic animals to survive.Besides sunlight and C02,algae growth also depends on nutrients like phosphorus and nitrogen.

unable to support most forms of aquatic life.This strange annual curse isn dead zones like this one have formed all over the world.But to explore what creating these lethal conditions,we first need to understand how a healthy marine ecosystem functions.In any body of water that receives sufficient sunlight,plant-like organisms such as algae and cyanobacteria thrive.

For most of the year, the Gulf of Mexico is teeming with marine life,from tiny crustaceans to massive baleen whales.But every summer, disaster strikes.Around May, animals begin to flee the area.And soon, creatures that can swim or can swim fast enough begin to suffocate and die off in massive numbers.From late spring to early autumn,thousands of square kilometers along the coast become a marine dead zone.

That doesn't mean the test itself is worthless n fact, it does a good job of measuring the reasoning and problem-solving skills it sets out to.But that isn鈥檛 the same thing as measuring a person potential.Though there are many complicated political, historical, scientific,and cultural issues wrapped up in IQ testing,more and more researchers agree on this point,and reject the notion that individuals can be categorized by a single numerical score.

Today, IQ tests employ many similar design elements and types of questions as the early tests,though we have better techniques for identifying potential bias in the test.They are no longer used to diagnose psychiatric conditions.But a similarly problematic practice using subtest scores is still sometimes used to diagnose learning disabilities,against the advice of many experts.Psychologists around the world still use IQ tests to identify intellectual disability,and the results can be used to determine appropriate educational support,job training, and assisted living.IQ test results have been used to justify horrific policies and scientifically baseless ideologies.

Instead, the cause was likely environmental mproved education, better healthcare, and better nutrition.In the mid-twentieth century,psychologists also attempted to use IQ tests to evaluate things other than general intelligence,particularly schizophrenia, depression,and other psychiatric conditions.These diagnoses relied in part on the clinical judgment of the evaluators,and used a subset of the tests used to determine IQ practice later research found does not yield clinically useful information.

In Nazi Germany, the government authorized the murder of children based on low IQ.Following the Holocaust and the Civil Rights Movement,the discriminatory uses of IQ tests were challenged on both moral and scientific grounds.Scientists began to gather evidence of environmental impacts on IQ.For example, as IQ tests were periodically recalibrated over the 20th century,new generations scored consistently higher on old tests than each previous generation.This phenomenon, known as the Flynn Effect,happened much too fast to be caused by inherited evolutionary traits.

Without taking into account that many of the recruits tested were new immigrants to the United States who lacked formal education or English language exposure,they created an erroneous intelligence hierarchy of ethnic groups.The intersection of eugenics and IQ testing influenced not only science,but policy as well.In 1924, the state of Virginia created policy allowing for the forced sterilization of people with low IQ scores decision the United States Supreme Court upheld.

At that time, many people believed in eugenics,the idea that desirable and undesirable genetic traits could and should be controlled in humans through selective breeding.There were many problems with this line of thinking,among them the idea that intelligence was not only fixed and inherited,but also linked to a person race.Under the influence of eugenics,scientists used the results of the military initiative to make erroneous claims that certain racial groups were intellectually superior to others.

And that left the door open for people to use the test in service of their own preconceived assumptions about intelligence.What started as a way to identify those who needed academic help quickly became used to sort people in other ways,often in service of deeply flawed ideologies.One of the first large-scale implementations occurred in the United States during WWI, when the military used an IQ test to sort recruits and screen them for officer training.

Questions were adjusted for each age group,and a child score reflected how theyperformed relative to others their age.Dividing someone score by their age and multiplying the result by 100 yielded the intelligence quotient, or IQ.Today, a score of 100 represents the average of a sample population,with 68% of the population scoring within 15 points of 100.Simon and Binet thought the skills their test assessed would reflect general intelligence.But both then and now,there no single agreed upon definition of general intelligence.

In 1905, psychologists Alfred Binet and The odore Simon designed a test for children who were struggling in school in France.Designed to determine which children required individualized attention,their method formed the basis of the IQ test.Beginning in the late 19th century,researchers hypothesized that cognitive abilities like verbal reasoning,working memory, and visual-spatial skills reflected an underlying general intelligence, or g factor.Simon and Binet designed a battery of tests to measure each of these abilities and combine the results into a single score.