(A) The reasons for conserving biodiversity can be grouped into three categories:
$(a)$ Narrowly utilitarian,$(b)$ Broadly utilitarian,and $(c)$ Ethical.
$(a)$ Narrowly utilitarian: These reasons are obvious as humans derive countless direct economic benefits from nature. $(i)$ Food (cereals,pulses,fruits),firewood,fiber,construction material,industrial products (tannins,lubricants,dyes,resins,perfumes),and products of medicinal importance. $(ii)$ More than $25,000$ species of plants contribute to the traditional medicines used by native peoples around the world. At least $25$ percent of all drugs are currently sold across the market worldwide are derived from plants.
$(b)$ Broadly utilitarian: $(i)$ Biodiversity plays a major role in many ecosystem services that nature provides. $(ii)$ The Amazon forest is estimated to produce through photosynthesis $20$ percent of the total oxygen in the earth's atmosphere. $(iii)$ Pollination,without which plants cannot give us fruits or seeds,is another service that ecosystems provide through pollinators like bees,bumblebees,birds,and bats. $(iv)$ There are other intangible benefits that we derive from nature,such as aesthetic pleasures of walking through thick woods,watching spring flowers in full bloom,or waking up to a bulbul's song in the morning.
$(c)$ Ethical: $(i)$ We share this planet with millions of plant,animal,and microbe species. $(ii)$ Philosophically or spiritually,we need to realize that every species has an intrinsic value,even if it may not be of current or any economic value to us. $(iii)$ We have a moral duty to care for their well-being and pass on our biological legacy in good order to future generations.