Lecture 19

• global temperatures are rising with direct effects on species distributions
• the Arctic is getting greener as the tundra is being taken over by plants that are not as suited to the cold
• altitudinal range shifts are possible but the suitable habitat has a limited area
• habitat fragmentation


  the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay
• some of the last great rainforests are being wiped out
• fires are often used to open-up the dense forest
• Indonesia has lost billions of hectares of forest since 2000
• in response to the habitat loss the worlds biodiversity is vanishing fast
• one in four species are at risk of extinction
• 40% of amphibians, 34% of conifers, 33% of reef corals, 31% of sharks and rays, 25% of mammals and 14% of birds are at risk of extinction
• massive insect decline threatens collapse of nature
• Dodo, great auk, Yangtze river dolphin, Pyrenean ibex are all extinct to name a few
• numbers of Bornean orangutan have more than halved in the past 60 years
• the south China tiger is gone from the wild with only 100 in captivity in 2015
• numbers of giant panda increased enough for the IUCN Red List to downgrade it from endangered to vulnerable in 2016
• Hawksbill sea turtles are critically endangered due to tortoiseshell trade, collection of their eggs for food, and destruction of coral reefs
• species richness is a matter of space
• a mathematical model to describe the species-area relationship:

  S=cA^z

  • S = the number of species
  • A = the habitat area
  • z = the slope of the species-area relationship
  • c = the intercept with the y-axis
• species richness is a matter of time
• species richness is a matter of isolation
• island biogeography


  a field within biogeography that examines the factors that affect the species richness and diversification of isolated natural communities
• the rate of new species arrivals drops as species accumulate
• extinction rate increase with competition
• rates balance each other at the point of equilibrium
• classical biogeography:

  • observation of ecological and other biophysical factors that affect the distributions of species and of biotic communities or ecosystems;
  • examination of historical happenings and evolutionary mechanisms that changes those species and their distributions through climate change, plate tectonics, species interactions, or other events and processes
• conservation biogeography uses both paradigms of conservation biogeography to examine the implications of past and present distributions in order to plan for the protection of biodiversity under current and possible future conditions
• metapopulations


  consists of a group of spatially separated populations of the same species which interact at some level