Question

what will happen if lions are totally killed in a forest

Answer 1

If lions are killed all together it will affect the ecosystem in a variety of ways which will lead to imbalance in ecosystem . THAT is if we kill all the lions, the secondary consumer trophic level experiences a loss due to which the primary consumers (deers ,rabbits,zebra etc) increase in number because there is no one to check their count.As a result the producers (plants) will be eaten or will be grazed well and this to a decrease in their level.So ultimately plants  decrease which will affect the climate of that place.Also aftersome time the primary producer level may also go down to due unavailability or limited food resource.

Answer 2

If lions will be no more than who will eat all the herbivores animals and becayse of which the population of herbivores will increase rapidly and than the herbivores animals will eat all the plants. and there will be no trees left on the earth.