Chapter 14: Why is the World Green?

Chapter 14: Why is the world green? Let’s assume a population with a diet of 90% grain National Focus Increase grain production Prevent the loss of grain Sparrows are eating the grain Let’s make it a national mission to eradicate sparrows What could possibly go wrong? Food Chains 3 b...

Chapter 14: Why is the world green? Let’s assume a population with a diet of 90% grain National Focus Increase grain production Prevent the loss of grain Sparrows are eating the grain Let’s make it a national mission to eradicate sparrows What could possibly go wrong? Food Chains 3 basic levels Producers: plants Herbivores: plant eaters Carnivores: eat the herbivores Bob Paine Introduced to Ecology by a professor that asked “Why is nature green is everything eats the plants? General Convention Each level limited the next higher level Plant availability limited herbivores Herbivores limited the predators Food webs were regulated from the bottom up Bob Paine’s hypothesis Herbivores were controlled from the top down Predators controlled herbivores Herbivores controlled plant Mukkaw Bay in Washington Tide Pools Animal organized into bands Acorn barnacles Mussells Snails Starfish Starfish was primary predator Are starfish affecting lower levels of food chain? Experimental design Chose a 150 square foot area Removed starfish with a crowbar Tossed them far away into the bay Results Mussel population increased 4 algal species disappeared Community diversity reduced from 15 species to 8 Predator stabilized community by controlling competitive species Keystone species Species that regulated diversity in ecosystems Removal of keystone can cause community collapse Jim Estes, Aleutian Islands Were otters supporting the kelp or kelp supporting the otters? Observation Reduced kelp beds when otters absent Fur trading reduced in 1911 Otter species came back in some islands but not others Conclusion Otters rebounded Reduced urchins Increased kelp Increased fish and seabirds Otters absent Increased urchins Greatly reduced kelp Otters were keystone species Sparrows are eating the grain Let’s make it a national mission to eradicate sparrows What could possibly go wrong? Everything There was an explosion of locusts This led to a famine that killed millions