When species disappear or fall in number, ecosystems and people—especially the world's poorest—suffer. Biodiversity is especially important to the poor—75% of whom live in rural areas and depend on nature for their food and livelihoods. If there are no animals in forests, then there will be a lack of Carbon Dioxide which is required by Plants for Photosynthesis. If plants wont be able to do photosynthesis to get food,then they will die, resulting in lack of oxygen in that place, and slowly the Humans and Animals would finish due to the lack of oxygen.As we are all part of the ecosystem, hence if we don't have animals, we would all die. Humans and plants are dependent on animals for the fulfillment of their varied needs, however, animals are not dependent on humans. Research shows that the physical and mental health of humans is closely related to access to nature.