Threats to Biodiversity chap 3 “Extinction is the most irreversible and tragic of all...

Threats to Biodiversitychap 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”Michael Soule, 2004

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


• Major factors impacting biodiversity


• Habitat Degradation• Includes conversion from suitable to

unsuitable, lowering quality, fragmentation that lower PVA

• Causes: many industries (e.g. forestry, agriculture, development, fishing, mining, chemical)


• Overexploitation• Hunting, collecting, fishing (and

indirect by-catch), trade of animals (and parts)


• 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)


• 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


• “Snowballing” effect of the invasion of the alien root pathogen


• “Snowballing” effect of the invasion of the alien root pathogen

• Indirect effects


• 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)


• Toxic chemicals (PCB’s and dioxins) accumulate in fatty tissues

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)


ecosystems• Early extinctions probably caused by

overexploitation • Now, habitat degradation and/or

invasive species major factors


ecosystems• No. of genera (megamammal) extinct

and cause• 72% Aust• 88% NAm


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


ecosystems


ecosystems• Since 1500, >129 sp extinct• Habitat loss major cause• Invasive sp contributed for many• Overexploitation for 1/5

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


• Tambalacoque & Dodo


• E.g. sea otters and sea urchins


http://www.google.com/imgres?imgurl=http://www.sciencedaily.com/images/2008/01/080111151504-large.jpg&imgrefurl=http://www.sciencedaily.com/releases/2008/01/080111151504.htm&h=399&w=600&sz=126&tbnid=d0qp3fF3DpwJ::&tbnh=90&tbnw=135&prev=/images%3Fq%3Dpollock%2Bfish%2Bpic&hl=en&sa=X&oi=image_result&resnum=2&ct=image&cd=1

http://www.google.com/imgres?imgurl=http://www.pac.dfo-mpo.gc.ca/sci/herring/hertags/images/herring_venus.jpg&imgrefurl=http://www.pac.dfo-mpo.gc.ca/sci/herring/hertags/pages/default4_e.htm&h=563&w=750&sz=60&tbnid=1JTj7xcHw7kJ::&tbnh=106&tbnw=141&prev=/images%3Fq%3Dherring%2Bpic&sa=X&oi=image_result&resnum=3&ct=image&cd=1


• Another problem is the removal of top predators, which may cause the ‘ecological release’ of mesopredators

http://www.google.com/imgres?imgurl=http://bp1.blogger.com/_vdI2KXwkaoc/Rt_fu7-1igI/AAAAAAAAAcU/0omPNKiUfM0/s320/raccoon2.jpg&imgrefurl=http://gowanuslounge.wordpress.com/2007/09/06/biting-prospect-park-raccoon-gets-death-penalty/&h=289&w=313&sz=31&tbnid=Hgdct3iE520J::&tbnh=108&tbnw=117&prev=/images%3Fq%3Draccoon%2Bpic&sa=X&oi=image_result&resnum=2&ct=image&cd=1

http://www.google.com/imgres?imgurl=http://www.taiko.org.nz/Cat02.jpg&imgrefurl=http://www.taiko.org.nz/Taikotuku.html&h=396&w=446&sz=59&tbnid=Ze-cE_3HCJsJ::&tbnh=113&tbnw=127&prev=/images%3Fq%3Dferal%2Bcat%2Bpic&sa=X&oi=image_result&resnum=1&ct=image&cd=1

http://www.aaanimalcontrol.com/gallery/opossum015.jpg


• 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)


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)

http://www.redlist.org/

Current Pattern of Global Endangerment



• What groups are in endangered?

Turtles at 42%


• Globally threatened processes• Some dramatic phenomenon may

disappear (e.g. large-scale migrations)

• Read Essay 3.3


• Factors threatening biodiversity• Factors are listed in the Red List• Knowledge varies tremendously and

by taxonomic group and habitat• Most face multiple threats and

threats can act synergistically


• Overexploitation is major cause for fish


• 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


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)


• Proportion of sp threatened in US


• Examining threats to US sp

A correlative cause of many of these factors is urbanization


• 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)



• What types of sp are most vulnerable?

• Through studies, we have determined there are ‘suites’ of characteristics that make some sp more vulnerable

• E.g. large range requirements, narrow habitat range, rarity, low reproductive rate, extreme specialization or co-evolutionary dependancies


• Vulnerability due to Specialization• Many species (especially tropical)

have narrow environmental ranges and highly specialized diets or habitats

• Perturbations can easily disturb them• Specialization on other species can

be precarious as well


• 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


• 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?


vent sp

raptors seabirds

batsIsland sp

big cats


• 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


• Island communities have relatively high rates of endemism, although communities maybe less rich than comparable mainland sites

• However, many island biotas are frequently endangered; why?


• Case Study: birds of Channel Islands• 80 year comparison of pop(s)

– 40% of small pop(s) went extinct (<10 bp)

– 10% of pop(s) with 10-100 breeding pairs

– 1 population of 100-1000 bp– No pop(s) if >1000 bp


• “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


• 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)


• 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


• Responses to the Biodiversity Crisis• Conservationists and developers

agree where solutions need to come from:– 1) scientific analysis and promotion of

the causes of biodiversity change– 2) technological improvements– 3) legal and institutional instruments– 4) economic incentives and plans– 5) social interventions


• Solutions will include: – Establishing protected areas– Targeted interventions at the genetic,

species, and ecosystems levels– Restoration of damaged ecosystems– Recovery of endangered species– Creation of sustainable forms of

development


• 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 geographicalpriorities and “how” questions about developing and implementing strategies to conserve conservation targets at priority places Redford 2003

Laws and International Agreements

• One major tool for conservationists are US laws and international agreements

• Please Review Case Study 3.3!!

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


• 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


• Overall, birds down 7%

• Albatrosses and petrels down 25%


• Unfortunately most species groups are too poorly known to adequately evaluate trends

• However there are a number of indicies attempting to bridge these gaps

• IBI (index of biotic integrity), LPI (living planet index; pop change of 1100 terrestrial, marine, and freshwater vertebrate sp)


• Terrestrial sp (A) and broken down


• 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)


• Projected trends• Dark most impact


• In the end, it is essential we better understand the factors that drive human behavior, which ultimately drive the causes of biodiversity loss


Date post:	18-Dec-2015
Category:	Documents
Upload:	emmeline-evans
View:	224 times
Download:	1 times

Threats to Biodiversity chap 3 “Extinction is the most irreversible and tragic of all...

Documents