endangered species/ protect and save/ future generations/ experience/ their presence and value//

Endangered species should be protected and saved; therefore, future generations can experience their presence and value.

Endangered species could be protected and saved; as a result, future generations can experience their presence and value.

Endangered species have to be protected and saved since future generations can experience their presence and value.

Endangered species must be protected and saved so that future generations can experience their presence and value.