Wouldn't it make more sense to just donate to a project that plants trees? Ecosia profits from ads, increases that profit by allowing Google and Bing (Microsoft) to track their users, and then invests the profit in planting trees. You're paying for tree planting with your data and your clicks on ads.
Kagi's philosophy is, to an extent, the antithesis of that: it does not show ads or track users; its revenue comes mainly from subscriptions. Kagi would need to increase subscription prices if it were to start seriously donating to a tree-planting initiative. At that point, isn't it better to let interested users donate to whatever causes they see fit based on their worldview and financial availability?