Sure, let's arrange these words/phrases into correct sentences.
'If we don't protect the climate, most living species will disappear.'
This sentence is about the necessity of protecting our climate to prevent the extinction of many living species.
'Humans are to blame for global warming since they are destroying the rainforests.'
This sentence discusses the role of humans in contributing to global warming by destroying rainforests.
'Many species have become extinct because they have lost their natural habitats.'
This indicates that the loss of natural habitats has led to the extinction of many species.
'Whales and dolphins are declining in numbers due to sea pollution.'
Highlighting how sea pollution is causing a decline in the population of whales and dolphins.
'According to research, humans are responsible for the extinction of countless species.'
This sentence suggests that scientific research has identified humans as a major cause of species extinction.