Threats to Biodiversity - Introduction to Conservation Biology - Lecture Slides, Slides of Biology

Download Threats to Biodiversity - Introduction to Conservation Biology - Lecture Slides and more Slides Biology in PDF only on Docsity! Threats To Biodiversity chap 3 “Extinction is the most irreversible and tragic of all environmental calamities. With each plant and animal species that disappears, a precious part of creation is callously erased” Docsity.com Threats to Biodiversity • As our numbers climb, we expand agricultural conversion, import invasive species, hunt more species, degradate habitat, fragment and lose habitat, pollute water and air, impact climate… • In short, we are causing the 6th mass extinction, the only biological driven one Docsity.com Threats to Biodiversity • Overexploitation • Hunting, collecting, fishing (and indirect by-catch), trade of animals (and parts) Docsity.com Threats to Biodiversity • Invasive Species • With our help, species have the ability to get virtually anywhere in the world • Direct actions: predation, parasitism, disease, competition or hybridization • Indirect paths: changing abundances, disruption of mutualisms, modifying habitat, reducing habitat quality) Docsity.com Threats to Biodiversity • Anthropogenic Climate Change • Climate has been a cause of previous mass extinctions • Couple this with lower abundance, invasive species and other problems, a severe impact is likely from climate change • Climate change will also trigger additional biological responses (e.g. malaria in temperate places)…Fig 3.3 Docsity.com Threats to Biodiversity • Anthropogenic Pollution • There are direct discharges of chemicals into the environment, there are also pollutants released into the atmosphere • Toxic chemicals (e.g. mercury, lead) are found even in remote areas • Also have the problem of bioaccumulation (or biomagnification) Docsity.com Threats to Biodiversity • Toxic chemicals (PCB’s and dioxins) accumulate in fatty tissues Docsity.com Anthropogenic Extinctions… impact on communities and ecosystems • Loss of species, populations and/or habitat is dramatic and extreme • Extinction as a process… • Can be local or global (also, ecological) Docsity.com Anthropogenic Extinctions… impact on communities and ecosystems • Consider Polynesian colonization of Pacific Islands 1-3KYA • Over 2000 species of birds (flightless rails) and 8000 populations driven to extinction • Story is not so simple… • Where invasive sp and habitat degradation combined, extinction followed Docsity.com Anthropogenic Extinctions… impact on communities and ecosystems • Since 1500, >129 sp extinct • Habitat loss major cause • Invasive sp contributed for many • Overexploitation for 1/5 Docsity.com Anthropogenic Extinctions… indirect impacts • Species don’t exist in a vacuum and extinctions usually have a ripple effect • ‘Cascade effects’ such as secondary extinctions may occur • E.g. plants with a single sp pollinator or seed dispersers • E.g. sea otters and sea urchins Docsity.com Anthropogenic Extinctions… indirect impacts • So there are many important species in a given community and some are more important than others • Dominant sp: common, but also have strong effects on other members • Ecosystems engineers: those that modify the ecosystem (e.g. beaver, elephant) • Keystone sp: sp that has more impact on community than numbers (biomass) would suggest (e.g. bat pollinator) Docsity.com Current Patterns of Global Endangerment • Best data on global endangerment are collated in the IUCN Red List of Threatened Species (www.redlist.org) • All species placed into one of 9 categories (3 primary categories: Critically Endangered, Endangered, Vulnerable) • To date, only 2.5% of species evaluated (and 41% considered endangered) Docsity.com Current Pattern of Global Endangerment • Globally threatened processes • Some dramatic phenomenon may disappear (e.g. large-scale migrations) • Read Essay 3.3 Docsity.com Current Pattern of Global Endangerment • Where are sp most at risk worldwide? • Not all biomes (and their inhabitants) are equally at risk • Most tropical habitats and grasslands have large substantial numbers of threatened vertebrates Docsity.com Current Pattern of Global Endangerment…the US • Geographically, there are very high numbers in SAm, SE Asia, sub-Saharan AF, Oceania, and NAm (where?) • The US is second (Ecuador) for the number of species though to be at risk of extinction globally (IUCN) • Many are plants (>5000sp), freshwater species (e.g. mussels {70%},crayfish, stoneflies) Docsity.com Current Pattern of Global Endangerment • Threatened species in other countries • Unfortunately, many countries lack solid data on what and how many sp are actually in trouble • Some countries have a high proportion of the flora and fauna at risk • E.g. Madagascar 80% of plants and 30% of vertebrates (case study 3.2) Docsity.com Current Pattern of Global Endangerment • Top carnivores with low densities, large ranges, large body size, are often cited as being vulnerable to habitat degradation, as well as overexploitation • For marine animals, body size itself does not appear to be a problem, but is associated with another… low reproductive rate Docsity.com Current Pattern of Global Endangerment • Vulnerability of Rare species • Why might a species be rare? – Consider 3 characteristics: geographic range, habitat breadth and abundance • How might each influence vulnerability? • How might they interact? Docsity.com Current Pattern of Global Endangerment • Let’s consider a case of extreme endemism: ‘Centinela Ridge’ in Ecuador • During a RAP inventory, 90 endemic plant species were discovered • Immediately following the inventory, entire ridge cleared for agriculture Docsity.com Current Pattern of Global Endangerment • “Bad luck” species do not have intrinsically vulnerable traits, just bad luck • For example, many freshwater fish near large cities are vulnerable, whatever their LHC • 50% of variation in extinction risk for primates and carnivores is strictly due to anthropogenic distrubances Docsity.com Current Pattern of Global Endangerment • Economic and Social Context • Economic growth and rising affluence drive habitat conversion and overexploitation • Unfortunately in the US, areas of high endemism and richness are areas of high human growth (e.g. s. CA, e-c TX, s FL) Docsity.com Current Pattern of Global Endangerment • At the other end of the economic spectrum, billions live in poverty – 1B < $1/day – 2.7B < $2/day • As a result, unsustainable levels of burning, small-scale agriculture, grazing and bushmeat hunting occur wherever these practices help people survive Docsity.com Current Pattern of Global Endangerment • Single-species approaches will not be enough to conserve ‘biodiversity’…larger spatial scales are going to be needed • However, many conservation actions are achieved at smaller scales (i.e. local) • Need to prioritize and plan at larger scales (consisting of local partners) Conservationist’s are generally asking “where” questions to set geographical priorities and “how” questions about developing and implementing strategies to conserve conservation targets at priority places Redford 2003 Docsity.com Driving Factors and Trends in Species Endangerment • The first step is identifying a trend • The second step is to determine what factors most influence trends • Finally, establish a plan to remove or eliminate the identified threats • As easy as they sound, none of these steps are as easy as they appear and the further along, the more ‘external’ factors enter the process Docsity.com Driving Factors and Trends in Species Endangerment • Besides developing a plan for a single species, important to track ‘status’ trends to determine success • The Red List Index tallies changes in status due to either a deterioration or improvement of all threatened species Docsity.com Driving Factors and Trends in Species Endangerment • It is not enough to determine where changes are occurring (reactive), but rather perhaps we can use information to generate predictive models of what species or systems may be more vulnerable than others (proactive) Docsity.com Driving Factors and Trends in Species Endangerment • In the end, it is essential we better understand the factors that drive human behavior, which ultimately drive the causes of biodiversity loss Docsity.com