What do you think will be the world's greatest challenges in 2050?
Please rank the top three challenges. Order the items from the following list. First select an item with the spacebar to show a menu of possible ranking positions. Next, click a ranking position to order it in the ranked list. Note the menu will display more ordering options as you add items to the ranked list.
Drag items from the left-hand list into the right-hand list to order them.