Since the sale of the platform formerly known as Twitter in October 2022, almost half of its 'environmentalist' users – including scientists, policymakers and activists – have stopped tweeting.

US researchers compared the habits of 380,000 people who tweeted regularly about environmental issues with a control group of 458,000 users who tweeted about the upcoming US presidential election.

The researchers chose the 2020 election topic to define a control sample based on it being frequently and broadly discussed, indicating it should represent a general sample of Twitter users.

They found the active Environmental Twitter community (defined as those who posted at least one tweet on the topic in a 15-day period) had declined by 47.5 percent by April 2023.

The authors of the study note this is a significantly higher dropout rate than the population as a whole, expressing concern about the consequences for public discourse and environmental activism.

At just 20.6 percent, the decline was much less severe among the users the authors referred to as Politics Twitter.

The new research builds on the findings of a 2022 study conducted by some of the same team, which analyzed the Twitter activity of 1 million environmentally-engaged people, seeking to understand the factors that influence people's conservation attitudes.

"We found six different personas based on interests in biodiversity conservation, public lands or climate change mitigation," says biologist and environmental analyst Charlotte Chang from Pomona College, lead author of both studies.

Twitter has been the most popular platform for environmentalists to collaborate on advocacy goals, share ideas and research, and find new ways to work together.

"We saw that there was a vibrant community engaging in discourse around environmental topics," Chang says.

"This then raised the question of how this community may be impacted by changes to Twitter's governance."

Social media platforms that resemble Twitter currently have significantly smaller user bases. So the team suggests any change in how users who care about the environment interact with the site raises serious questions about how to get people who care about the environment to work together.

"The rapid decline in active users raises alarm bells and signifies a substantial loss for the conservation community," the authors of the new study write.

The reduction in use by environmental researchers and activists also risks exacerbating social divides, as groups further isolate themselves from different viewpoints on entirely different platforms, rather than just in different networks within the same platforms.

In a recent survey by Nature of over 9,000 scientists who used Twitter, more than half said they spend less time on the platform now than they did six months ago, and nearly 7 percent said they no longer use it at all.

Some of the researchers surveyed mentioned they had seen an increase in trolls, hate speech and fake accounts on Twitter. Environmental scientist Žiga Malek from the Free University of Amsterdam, reported encountering many "strange" political far-right accounts promoting science denialism and racism, and having to constantly block them.

"In the past few months, since the takeover and changes at Twitter, the amount, vituperativeness, and intensity of abuse has skyrocketed," hydroclimatologist Peter Gleick told AFP.

About 46 percent of the Nature survey respondents had joined other social platforms like Mastodon, Bluesky, Threads, and TikTok.

If people who care about the environment leave Twitter for these alternatives, Chang and colleagues suggest advocates and researchers will have to be quick to adapt. For example, by tracking which platforms environmental voices are using or a broad campaign to migrate supporters to a new platform to continue information exchange, mobilization, and research.

"Such changes amplify the need to create collaborations across industry, the non-profit sector, and academia," the authors conclude, "to track public engagement with the environment across social media platforms for the benefit of primary research, applied environmental conservation, and climate mitigation."

The new study was published in Trends in Ecology and Evolution and the survey in Nature.