MICHELLE NICHOLS  BRITISH naturalist David Attenborough warned on Tuesday that climate change is the biggest security threat that modern humans have ever faced, telling the U.N. Security Council: "I don't envy you the responsibility that this places on all of you." Attenborough, 94, the world's most influential wildlife broadcaster, addressed a virtual meeting of the 15-member council on climate-related risks to international peace and security, chaired by British Prime Minister Boris Johnson. "If we continue on our current path, we will face the collapse of everything that gives us our security: food production, access to fresh water, habitable ambient temperature…