science-based conservation

Question 1

aims and approaches

Answer 1

• aim is to identify species and populations at greatest risk of extinction so to target funding effectively and act appropriately
• declining population paradigm, seek to understand the causes of species decline
• small population paradigm, seek to understand the negative consequences of existing in a small population (more vulnerable to random events and genetic effects)

Question 2

problems with a small population size

Answer 2

• vulnerable to random events
  e.g. fluctuations in sex ratio or age distribution, disease outbreaks, unusual weather events
• vulnerable to genetic effects
  e.g. inbreeding depression (results in reduced individual fitness), genetic drift (results in loss of genetic diversity, inability to adapt)

Question 3

habitat loss

Answer 3

• major cause of species decline but not usually directly responsible for species extinction
• strong relationship between size of habitat area and biodiversity
• direct result of economic development and human population growth
• requires understanding of economics, sociology and psychology and engagement with population planning in order to mitigate effects

Question 4

species-area relationship

Answer 4

• as the area of a habitat increases, number of species increases
• derived from study of islands
• equilibrium between rate of extinction and immigration, smaller islands have less immigration and smaller population sizes so a higher risk of extinction, therefore have lower biodiversity
• applies to any area of habitat
• allows prediction of extinction rate when habitat is lost

Question 5

species-area relationship, model of habitat loss in a rainforest

Answer 5

• fragments of rainforest of 1, 10 and 100h left to study when deforested
• animals at high trophic levels and animals who need a large foraging area left first
• often have a large influence on other species
• substantial loss of dung beetle diversity in small habitats from a lack of large vertebrate dung
• biodiversity decline 50% in 1ha, 30% in 10ha and 15% in 100ha

Question 6

habitat fragmentation

Answer 6

• breaking up habitat into large number of small habitat patches
• reduces overall amount of habitat available
• ‘edge effect’, more edge habitat, less interior habitat
• will affect species differently depending on habitat preferences
• specialised interior species lost
  e.g. edges of tropical rainforests drier and more exposed, biodiversity is lower, specialised interior plants cannot survive
• increases isolation of habitat patches, species reluctant/incapable of crossing areas between habitats leads to genetic isolation, areas not recolonised after extinction event, creates metapopulations

Question 7

habitat matrix

Answer 7

• fragments of higher quality natural habitat surrounded by areas of human modified lower quality habitat
• adaptability to lower quality habitat depends on species
• landscape management enables species to migrate between habitat fragments
  e.g. wildlife corridors, ‘green bridges’ over roads, improving quality of human matrix habitat

Question 8

5 main causes of species decline

Answer 8

• habitat loss
• invasive species/ diseases
• climate change
• direct use
• pollution

Question 9

how much habitat is enough?

Answer 9

• scientific approach, develop models to predict area required to sustain long term viable populations
• in reality non-scientific criteria usually used to establish size, location and shape of nature reserves such as political, land ownership, where ‘spare land’ is
• often contested whether one large habitat block or several small areas is best

Question 10

monitoring habitat destruction

Answer 10

• remote sensing using satellite technology
• can monitor in real time and alert authorities quickly
  e.g. detecting forest fires in Amazon being used to illegally clear land
• problem is then enforcing laws and preventing habitat destruction

Question 11

metapopulations

Answer 11

• many sub-populations occupy habitat fragments
• may be connected by migration to a greater or lesser extent (connectivity reduces risk of extinction through recolonisation)
• conservation management strategies may focus on a single sub-population or whole meta population, threats may be different
• landscape scale conservation, reserve networks, reintroductions, translocations, reserve corridors

Question 12

metapopulations, Checkerspot butterflies

Answer 12

• coastal California
• one large population >400,000 ind.
• many small populations <500 ind.
• unusual weather events can eliminate all small populations simultaneously
• large population persists, source of recolonisation
• conservation focuses on large population

Question 13

impacts of climate change

Answer 13

• rapid, species may not be able to adapt or move quickly enough
• habitats already destroyed and fragmented, species cannot move ranges in response to climate change

Question 14

bioclimatic envelope models

Answer 14

• shows relationship between species distribution and climate
• used to predict future species extinction in response to climate change

Question 15

population viability analysis

Answer 15

• estimate probability of population surviving over a given time period
• calculate minimum population size necessary to survive over given time period
• allows for prediction of population decline in small populations and also determining whether a species is able to be saved

Question 16

how many species are there

Answer 16

• ~2m described species, majority invertebrates
• rate of description is low, lack of taxonomists
• 10-100m undescribed species
• many go extinct before they are described, especially in tropical forests (contain many unknown species but are being destroyed rapidly)

Question 17

IUCN conservation status required species information

Answer 17

• distribution
• population sizes
• population structure
• threats to long term survival

Question 18

thresholds for endangered species

Answer 18

• very significant reduction in population size, >70% in a 10 year or 3 generation period (longest)
• very significant reduction in geographical area, <5,000km
• estimated population size <2500 mature individuals with evidence of continued rapid decline
• estimated population size <250 mature
  individuals
• > 20% probability of extinction in the wild within twenty years or five generations (longer, up to max 100yrs) according to quantitative viability analysis

Question 19

why are so many endangered species vertebrates?

Answer 19

• bias, better data as they are large, charismatic, culturally important
• usually high trophic levels so more vulnerable to ecological disruption
• high levels of exploitation

Question 20

IUCN red list, extinction

Answer 20

• difficult to confirm that a species has become extinct
• extinct = no reasonable doubt the last individual has died
• extinct in the wild = individuals may survive in captivity/cultivation or outside the species historic geographical range