I give some TOPICS - some factors which can be combined into a TOPIC
there are many causes , factors that affect ecosystem - ecological system - directly or indirectly, slowly in time
storms, cyclones.. droughts and floods
population increase - increase in immigrations - increase in consumption
consumption of natural foods/services - consumption of industrial (artificial) foods/services
development of technology and science that changes or exploits balance in ecosystem, for individual profits
construction of too many dams across rivers, altering course of water..