User script to display estimated number of trees planted with Ecosia.

ecosia-trees.user.js

// ==UserScript==
// @name         Ecosia Trees Planted
// @namespace    481487dd5200e3aa69b16a9d80fa5f75
// @version      0.3
// @description  Display estimated number of trees planted with Ecosia.
// @author       Sam Saint-Pettersen <[email protected]>
// @match        https://www.ecosia.org/*
// @icon         https://s2.postimg.org/407qv942h/small-tree-icon-0.jpg
// @require      http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js
// ==/UserScript==

(function() {
    'use strict';
    $(document).ready(function() {
        let searches = $('.tree-counter-text').text(); // Get number of searches.
        const trees = Math.floor(parseInt(searches.replace(',', '')) / 45); // Calculate ~ trees planted.
        // Ecosia says that it takes around 45 searches to plant 1 tree.
        // Replace searches with estimate of trees planted.
        let noun = ' tree';
        if(trees < 1 || trees > 1) noun += 's'; // 0 trees, 1 tree, 2 trees, etc.
        $('.tree-counter-text').text('~ ' + trees + noun + ' (' + searches + ')');
    });
})();

https://imgur.com/a/mFDvK