Zuòwéi huánbǎo shìyè de zhīchízhě, tā cānjiā le hěn duō huódòng.
As a supporter of environmental causes, she participated in many events.
Tips
grammar
The 者 suffix turns verbs/verb phrases into 'person who does X': 支持 (to support) → 支持者 (supporter), 消费 → 消费者 (consumer), 工作 → 工作者 (worker). It's more formal than using 人.