A new study found unsafe amounts of mercury in fish and people in Puerto Maldonado, the capital of Peru’s southeastern Madre de Dios Region. Average mercury levels in nine of the 15 most commonly consumed fish species were above the limit recommended by the U.S. Environmental Protection Agency. Farmed fish had the lowest levels, according to Luis Fernández of the Carnegie Institution for Science’s Global Ecology Program at Stanford University in the United States, who led the study.

Seventy-eight percent of adults tested in Puerto Maldonado had levels that were more than twice the recommended limit for humans. The highest levels – three times the recommended threshold – were found in women of childbearing age. That is especially alarming, because mercury can damage the developing fetus’ neurological system.

 In a way, the results are not a surprise – accumulation of mercury from unregulated gold mining in waterways in Madre de Dios has been widely reported in recent years. But this is the most comprehensive study so far of the impact on fish and the humans who eat them, and it paints a stark picture that is hard to ignore. The study also busts some myths I’ve heard about mercury exposure in Madre de Dios:

Read more: 5 myths about mercury in Madre de Dios

Oil palm plantations in Kalimantan – the Indonesian name for the island known in English as Borneo – are expanding at the expense of forest, leading to an increase in carbon emissions, according to a study published October 7 in Nature Climate Change. The study found that 90 percent of the land converted to oil palm between 1990 and 2010 was forested. Nearly half of that area was intact forest, while the rest had been logged or was being used for agroforestry.

The study was led by Kimberly Carlson, a doctoral candidate at Stanford University, using a system designed by Gregory Asner of the Carnegie Institution for Science at Stanford. Asner has been using that system to map carbon stocks in the Peruvian Amazon, as well as in Colombia and Ecuador.

Read more: Can’t see the forest for the (palm) trees

We call our planet Earth, but we tend to forget that it is really mostly water. And what is the state of the world’s marine environments? A new Ocean Health Index gives the world an average score of 60 out of 100, based on the rankings of 171 countries. When I was in college, 60 was barely a passing grade. During a phone-in press conference today, some of the scientists who authored a paper on the index, published in Nature, said the good news is that there is room for improvement as countries work toward the “ideal” of 100.

Read more: World’s oceans get a barely passing grade

A new study shows that mercury from wildcat gold mining in the Peruvian Amazon is accumulating in the bodies of miners and other people in Peru’s southeastern Madre de Dios region. The analysis of mercury in hair samples reinforces a study by Peruvian health officials in 2010, which found high levels of mercury in some miners’ urine.

In the new study, published last week in the on-line journal PlosOne, Katy Ashe of Stanford University analyzed hair samples from 100 people (38 men and 62 women) in three mining camps and 104 people (60 men and 44 women) in Puerto Maldonado, the capital of Madre de Dios. The highest levels were found in men in the mining camps and in people who reported eating fish more than 12 times a month.

Read more: Telltale hairs reveal mercury in Peruvian miners’ bodies

Several small studies have shown that some fish in the Madre de Dios region in southeastern Peru contain dangerous levels of mercury. A larger study of mercury in fish and in people will soon get under way under the direction of Luis Fernández, a tropical ecologist from the Carnegie Institution for Science at Stanford University.

Read more: Would you like some mercury with that fish?