If you would like to open a page or an image in a new tab right from the search result page, you have two easy options.
Using the keyboard shortcut
Simply hold the ctrl and the alt/option key and left click on the image you would like to open in a new tab. The image will open in a new tab next to the one you are currently using Ecosia with.
Using your mouse
Right click on the image and choose "open image in new tab". However, some browsers don't offer this function, so the keyboard shortcut probably is the easiest to go by.