Earth has a really large population right now
Earth's population is concentrated in developing countries
recently population was increasing the fastest its ever had
nonparticipation: homeless people and immigrants don't have access or won't take it out of fear of being kicked out of US
sampling: limit the amount of information you take so it's reflective on the entire population (1 is more accurate in housing vs 2 that's more accurate for people that weren't included the first time)
too dry: can't farm and limited animals
wetlands: rain and heat make it hard to farm
cold lands: glaciers make it hard to farm and support animal life
mountains: high up it's snowy and hard to farm