Cika wannan jumla: A matsayin wani ɓangare na Greta Thunberg ta Makarantar yajin aiki don zanga-zangar sauyin yanayi, Foster ya gudanar da yajin aikin sauyin yanayi na mako-mako a gaban Fadar White House a Lafayette Square. A ranar 13 ga Satumba, 2019, Thunberg a matsayin wani ɓangare na tafiyarta ta Amurka zuwa
COP 25 a Santiago, Chile, ya shiga cikin yajin aikin Foster na White House wanda ya jawo dubbai zuwa shafin. A lokacin da yake a Jami'ar Harvard, ya gudanar da yajin aikin sauyin yanayi na mako-mako a kan matakan da ke gaban Widener Library tare da masu shirya Divest Harvard waɗanda suka yi kira ga jami'ar da ta ba da gudummawar su a cikin masana'antar mai. Ya taimaka wajen samun ƙarin sa hannu 186 don takardar neman su zuwa Jami'ar Harvard a cikin watanni 3 a wannan bazarar. Bayan da Foster ya dawo daga Jami'ar Harvard a ƙarshen 2019, Jane Fonda ta tuntube shi inda aka nemi ya taimaka ya kafa da kuma gina Fire Drill Fridays wanda ya kasance yajin aikin sauyin yanayi na mako-mako da aka gudanar a gaban Ginin Capitol na Amurka.