Directions: After reading the passage below, fill in the blanks to make the passage coherent and grammatically correct. For the blanks with a given word, fill in each blank with the proper form of the given word; for the other blanks, use one word that best fits each blank.
Loss of Biodiversity (生物多样性) Affects Human Society
If a species of bee disappears forever or a particular plant is extinct, what does it have to do with us humans? Well, according to a team of international scientists, biodiversity is dropping below levels (21) ______ (consider) safe for the health and happiness of human societies.
The issue is that everything is inter-connected and ecosystems support our societies (22) ______ they provide us with, for example, food, fibres and fuels. If species go on disappearing, this can disturb many vital processes (23) ______ crop pollination (授粉) and the decomposition (分解) of waste.
A framework which defines the environmental limits within (24) ______ humans can really operate -- called planetary boundaries -- says (25) ______ (lose) more than 10% of the biodiversity in an area places the local ecosystem at risk. Ecosystems are all different but this percentage is considered as a good measure of safety.
A study published in the magazine Science suggests that 58% of the world’s land surface (26) ______ (reduce) below this level already. These areas house 71% of the global population. Professor