I believe the answer is metabolism...
Answer:
Tundra
Explanation:
Ocean is the most stable biome, provides the majority of earths food and oxygen.
Rainforest provide 20% of earths food production. Also stable.
Grasslands although the don't get much rain it doesn't compare to the harsh weather that Tundra's face.
Tundra's is a very fragile environment. The freezing cold temperatures makes it a very difficult environment to survive in the winter, and plants and animals have a hard time coping with any extra stresses and disturbances. Therefore making it the least stable out of the rest listed.
Due to the increasing weather patterns, weather will become unpredictable and temperatures will rise which makes growing conditions worse
