Anno Fans - 1602: Food, Animals & Land

During droughts all crops will die - there is nothing you can do about this,
except wait. You do not need to replant drought-afflicted crops. A proportion
of special crop (Tobacco, Vines, Sugarcane, Cocoa, Cotton and Spice) fields
planted on islands with less than 100% suitability, will die.

Deer require a mixture of trees and open land to survive. Apparently even too many trees will kill them. Deer/elks
die when they eat Tobacco/Spices/Cotton/Sugarcrane, no matter if the balance
of wood-free fields still is good for them. Strangely they survive eating
wine.

Are patchy green/brown areas of land less fertile?

From the game's readme file: "Some islands not only have fertile topsoil, but
also desert and steppes. If you plant crops in one of these areas they will
grow more slowly."