Backing the parent comment, please see https://www.pbs.org/newshour/world/report-says-200-environme...
I vaguely recall a climate scientist disappearing under odd circumstances but I can't recall where. Maybe this was a scientist and activist in Latin America.
Ironic considering that the original claim was:
>Many climate scientists sounding the alarm get attacked and silenced (and activists get killed!)
But the source you provide only mentions "environmental and land defense activists".
Still, climate activists are routinely targeted: https://www.bbc.com/news/science-environment-63064471
I'm still vaguely recalling an article about a climate scientist disappearing under suspicious circumstances, but I cannot find it now.