What is biodiversity In general we consider a community to be diverse when it contains many different kinds of organisms Review What is biodiversity Can be measured in a variety of different ways Species Richness number of species in an area Species diversity combines richness with info on relative abundances of each species Functional diversity a measure of the diversity of a community in the components that influence how an ecosystem operates nitrogen fixers Can also measure diversity within species Genetic diversity total genetic information contained within all the individuals of a species the number and relative frequency of all alleles present in a species Why is biodiversity important Ecosystem services primary production nutrient cycling David Tilman tested whether increasing species richness and functional diversity in a community would affect net primary productivity in Minnesota prairies Tilman Experiments Hypothesis NPP increases with increasing species richness and with increasing functional diversity of species Experiment Plant 289 plots each with up to 32 species and up to 5 functional groups Species 1 functional group 2 species 2 functional groups 6 species 4 functional groups Conclusion NPP increases with increasing specie richness and increasing functional diversity of plants at least up to a point In other words biodiversity matters to ecosystem productivity Resistance to disturbance David tilman s research on prairie communities Field studies after severe drought in MN 1987 1988 A natural experiment Tilman had long term data on prairie communities before the drought he could monitor how the communities were affected by drought and how they recovered or failed to recover after the drought hypothesis resistance to disturbance should increase with increasing species richness Null there is no relationship between species richness and resistance Conclusion communities with higher species richness were more resistant to the drought Biodiversity can help to protect communities from disturbance Economic Benefits Wild plants fungi prokaryotes and animals have been the sources of a vast diversity of valuable products anti cancer drug Taxol derived from the yew tree Tillman s experiments showed that there is some redundancy in natural communities but now much disturbance and extinction before a tipping point is reached Review Patterns of Extinction Remember that there are 2 basic patterns of extinction Background extinction a default rate 1 10 per million years of loss of species due to normal levels of ecological and biotic turnover Mass Extinction events reflect cataclysmic planet wide environmental perturbations Present Day Rates of Extinction are approaching that of mass extinction events x100 to 1 000 background rate Associated with recent explosive growth of human population and associated impact on natural ecosystems Almost 50 of land surface area has been converted to human use pastural agricultural urban Over 505 of accessible fresh water is used for human consumption At current rates of extinction 50 of terrestrial plants and animals are in danger of disappearing by the end of the 21st century Not all Human Induced Extinctions are Recent End Pleistocene Megafaunal Extinctions 33 species of North American Large Mammals went extinct shortly after humans entered the continent and evidence is accumulating that human hunting pressure played an important role in this process Similar extinctions also occurred following human appearance in South America Eurasia Madagascar and Australia but not Africa DNA from Mammoth and Mastodon fossil teeth can be used to make an Elephant phylogeny incorporating living and extinct species Highly specialized Clovis spear points were made 11 13 000 years ago by early Americans and are found over much of the continent This advanced stone age technology was used to effectively hunt large game such as mammoths Megafaunal extinctions in Madagascar Humans colonized the island of madagascar from the African mainland and from what is now Indonesia only about 1000 years ago By 1500 CE all of the island s endemic megafauna was extinct Which terrestrial biomes have been most heavily impacted in terms of area by humans The Prairie Ecosystem The North American prairie is one of the most endangered ecosystems on Earth The grasslands of North America began to form about 20 million years ago but in some areas up to 99 of the prairie has been destroyed in just the last 125 150 years Although the ranges and population sizes of many prairie species have been severely degraded relatively few have been driven to extinction yet Greater prairie Chicken Populations have plummeted 10s of millions to 690K with habitat loss to agriculture Biodiversity Hot Spots Are Most Concern to Conservation Biologists A relatively small area with an exceptional concentration of endemic species and a large number of endangered and threatened species Note the large number oceanic islands the most vulnerable terrestrial ecosystems Oceanic Islands products of volcanic or tectonic uplift they have never had terrestrial connection to continental land masses Vulnerability endemic species radiations on oceanic islands have evolved in biotically sheltered conditions very few predators competitors parasites They are very vulnerable to introductions of novel competitors and predators from continental biotas Polynesia was the last part of the planet settled by humans These remote islands were especially rich in endemic species many restricted to single islands Fossil evidence on islands in the South Pacific suggests that about 2000 bird species many of them secondarily flightless species of rails were wiped out as people colonized this area Similar losses occurred in many other endemic groups of island animal and plants Hawaiian honeycreepers this monophyletic lineage is endemic to the Hawaiian Islands Of the 52 known species 18 were driven to extinction by Polynesian settlers 21 more after European colonization including 7 since 1990 13 species survive Ecological Impact of Human Settlement on a Pacific Island Mangaia Easter Island 800 years ago lush tropical paradise 10 000 people lived on the island 1722 Europeans found the island desolate treeless landscape 1 00 people living on island What Happened Evidence for an ecological disaster Humans overharvested resources on the island especially palm trees Soil erosion local extinction of many plants and animals The human population on