A Chrome extension. Displays how many trees your searches have planted (it's an estimate) and how many searchers until next tree is planted. There is also a version for Firefox: https://github.com/nake89/ecosia-count-trees
https://chrome.google.com/webstore/detail/ecosia-count-trees/ahfaljmpjgbkmbldipgdldgiiimdphec