In science news, an international research team published findings from its investigation of a destructive landslide that happened in northern India last winter. The disaster took place in February in the Himalayan state of Uttarakhand. It was triggered by a massive chunk of bedrock breaking apart from a high mountain peak. Heat from the high-velocity rockfall melted glacier ice in the mountains below and sent debris coursing through the river valley downstream. Most of the more than 200 people who were killed or missing were workers at two hydropower facilities that were damaged by the debris. The amount of rock and ice released in the avalanche was enough to cover Washington, D.C. to a depth of 6 inches. The researchers could not pin the event directly on a warming climate, but they noted that climate change does play a role in the stability of mountain slopes. They also said the disaster underscores the risk of hydropower development in geologically unstable terrain. The study was published in the journal Science.

In Canada, a community with longstanding water problems may soon be getting a clean drink. The province of Saskatchewan is attempting to secure federal funding to update the water treatment plant in Uranium City, a rural community that has been under boil-water advisories and drinking water warnings for 20 years. The CBC reports that $1.7 million would come from a federal infrastructure fund, which is currently upgrading other water systems in Saskatchewan.

In the United States, a binational program for monitoring airborne pollution found traces of PFAS chemicals in rain samples taken from sites around the Great Lakes. MLive reports that the monitoring program, which is jointly funded by the U.S. and Canadian governments, began testing for PFAS chemicals last August. For their PFAS analysis, researchers are monitoring five sites in a mix of urban and rural areas. So far the researchers are finding higher concentrations at the urban sites, which include Cleveland and Chicago. Industrial sites are likely the source of PFAS in the atmosphere. Once rain deposits the chemicals on land, they can trickle down and contaminate groundwater.

This week Circle of Blue reports on a toxic threat to the world’s coastlines.

Microscopic phytoplankton, which are the foundation of the marine food chain, are some of the world’s most abundant and ancient organisms. Though essential to ocean life, they produce plenty of drawbacks, too. When they cluster along the coast, certain species paint the nearshore waters in a palette of fiery reds and mossy greens. Other toxin-producing species cause beach closures, kill fish, and lead to restrictions on harvesting clams and oysters. A particularly devastating bloom on the Chilean coast in 2016 killed an estimated 27 million farmed salmon and trout.

Anecdotal evidence suggests that these marine harmful algal blooms are on the rise. But are they really increasing globally?

According to a first-ever assessment, the answer is no. More than 30 years of data did not provide a clear signal on a global trend. But that is also perhaps the wrong question to ask, says Gustaaf Hallegraeff, the study’s lead author. Understanding the risks posed by harmful algal blooms and their causes requires a narrower focus.

“Every region behaves differently,” Hallegraeff, an emeritus professor at the University of Tasmania, told Circle of Blue. “Every species behaves differently. We’re not making any progress if we try to combine all of that and make a prediction for the whole world. This work shows very clearly that we need to study this problem region by region and species by species. That’s the only way we can make progress.”

The UNESCO-backed study, which was published June 8 in the journal Communications Earth and Environment, is a sign of progress. Inspired by the UN’s collaborative effort to assess the consequences of climate change, the seven-year project brought together an international team of scientists to parse the data on marine harmful algal blooms.

Though lacking proof of a global trend, the study did find evidence of regional variations. Marine harmful algal blooms are decreasing along the west coast of North America and in Australia and New Zealand. The number of blooms is rising in the U.S. Gulf Coast, Caribbean, Central America, South America, northern Asia, northern Europe, and the Mediterranean. There was no trend along the east coast of North America or in Southeast Asia.

To do the analysis the team referenced two data sets. The first is a broad accounting of the occurrence of blooms worldwide. The other is narrower, documenting cases in which blooms caused economic or social harm. That data set includes more than 9,500 instances since 1985 where blooms closed beaches, killed fish, or poisoned people and shellfish. Around 200 algae species are known to produce toxins that are dangerous to aquatic life and humans.

By cross-referencing the data sets, the researchers found that the supposed global increase in blooms is due to better monitoring. In other words, we’re seeing more harmful algal blooms simply because we’re looking for them — and because more coastal development is putting more human activities in harm’s way.

One prominent example of coastal development is the dramatic rise of fish and shellfish farms. Global aquaculture production increased 16-fold between 1985 and 2018, which is the study’s period of analysis. More fish farms are leading to more awareness of the blooms, Hallegraeff said. Because they introduce huge volumes of nutrients into nearshore waters, fish farms might also be contributing to the blooms. But more data is needed to draw a firm conclusion for that connection, he said.

The study did not investigate freshwater harmful algal blooms, which are also assumed to be increasing globally because of more nutrients in lakes and rivers and warmer water temperatures. Hallegraeff said a similar research project for freshwater blooms would be relevant and welcomed.

That’s not the only item on the researcher’s to-do list. Hallegraeff said that the trend study is a starting point for further investigation. He wants to incorporate layers of data on climate change, nutrient inputs from aquaculture and agriculture, and ocean dynamics. Those factors could help to explain what is driving algal growth in certain regions. It could also aid in forecasting blooms.

“Can we better predict in the future what’s going to happen in those areas?” he said. “That is not easy work.”