Options for keeping the food system within environmental limits by Springmann, M, Clark, M, Mason-D'Croz, D, Wiebe, K, Bodirsky, B, Lassaletta, L, De Vries, W, Vermeulen, S, Herrero, M, Carlson, K, Jonell, M, Troell, M, Declerck, F, Gordon, L, Zurayk, R, Scarborough, P, Rayner, M, Loken, B, Fanzo, J, Godfray, H, Tilman, D, Rockström, J, Willett, W