Answer:
natural disasters,emigration and scarcity of food
Step-by-step explanation: natural disasters: this affect population where by organisms leave there area or habitat for another area due to unfavorable conditions eg. flood, bush fire, storms, earthquake etc. and can also lead to death.
Emigration:this is when organisms leave an area for another either in search of food, breeding purpose this reduses population where by organisms may never return.
scarcity of food:this occur when there is insufficiency or no food in an area which makes organisms leave their habitat for another in search of food and might even lead to death.