Sp and Landscape Conservation Frequently when it comes time to save or manage a species, nations...

Sp and Landscape Conservation

• Frequently when it comes time to save or manage a species, nations identify and protect critical habitat

• International treaties also tend to have a species-oriented approach (e.g. CITES)

• Conservation education tends to be species-oriented (e.g. pandas, wolves)


• Additionally, much of the information in conservation biology is focused on the individual species

• Even when taking a larger view, it is still simply counting species (e.g. hotspots, high endemic areas)

• Consequently, we will try to better understand small population biology


• Populations change: pop(s) are dynamic and are governed by 4 factors…

• Although the model of population change is relatively simple, identifying the process driving changes is not

• Some pop(s) are extremely consistent while others amaze us with their variation


• Organisms themselves may experience a relatively narrow view of the world (a generation of rotifer) while others perceive similar conditions for many generations (e.g. humpback whales)


• Many conservation biologists attempt to track populations using techniques and principles of population demography

• Demography focuses on the intrinsic factors that contribute to a population’s growth or decline, including age-dependent birth or death rates

• Other factors also influence population dynamics


• Sex-ratios, age-structure, and time of first reproduction influence pop dynamics (collectively termed LHC)

• E.g. Florida Key deer (small sub-sp) are largely restricted to a few islands

• Demographic study found mortality was skewed higher for males and 50% of those were car collisions

Mechanisms of Pop Regulation

• One question frequently asked is ‘why are some species rare?’

• This is important as we need to understand how mechanisms that influence population size can be manipulated to increase their size and maintain viable populations or rare sp


• Howard and Fiske (1911) introduced the concept of ‘catastrophic mortality factors’ and ‘facultative mortality factors’

• Density-independent and density-dependent factors also impact B


• Density-independent factors (a) and density-dependent factors (b&c)


• For density-dependent factors to regulated population growth, either per capita mortality must increase or per capita birth must decrease as population density increases

• General groupings of factors:– Inc D or dec B due to a less resources– Inc D due to inc predation, parasitism– Inc D or dec B to inc intrasp interactions


• Social behavior can play a direct role in regulating some animal populations, although they typically interact with resouce shortages (food, space)

• E.g. HOWR and BEWR


• Occasionally density and social behavior have the opposite effect in that B may increase or D may decrease at intermediate or high densities

• E.g. high densities help pollen transfer (Allele effect) or colonial nesters are more successful when large colonies


• No RS when density is <50


• Special Problems of Small Populations• There are 4 general causes of

extinction: genetic loss, demographic variability and declines, environmental variation and catastrophes

• Another threat is that of demographic uncertainty-such as changes in sex-ratio, RS, and mortality rates can all change rather quickly and randomly


• Environmental uncertainty can cause extinction in small pop(s) by causing a sudden increase in reproductive failure or individual mortality

• E.g. black stilt nesting biology in braided rivers


• Natural catastrophes can also have dramatic impacts on populations and should be accounted for

• E.g. reintroductions frequently occur on multiple sites to diminish the potential of a single catastrophic event eliminating all populations

Source-sink Concepts

• A metapopulation structured by source sink dynamics (not all sites equally likely to go extinct)


• It is important that conservationists distinguish between areas of high density and productive areas (van Horne 1983)

• Just theory? • Florida Key deer occur mainly on Big

Pine Key and another. Development has resulted in one end being a source (λ=1.02 vs. λ=0.87) with 15% dispersal


• Dynamics on Big Pine Key


• Peregrine falcons had dramatic declines due to ___

• Since then they have recovered, but not the coastal population


• Contrasting dynamics of N and Coastal pop(n)...urban pop(n) a pleasant surprise

Population was supplemented with translocated young; important due to poor dispersal


• The status of source-sinks can vary between years

• In good years, even ‘poor’ habitat may produce a surplus

• There is also ‘balanced dispersal’ in which movement may simply occur due to carrying capacity such that dispersal is due to saturated habitat, not necessarily a source

Metapopulations and Thresholds

• There has been relatively good evidence that this paradigm applies to a variety of organisms

• E.g. mountain lions and riparian corridors

• Read and understand Essay 12.1, 12.2, and 12.3


• There has been a number of theoretical advancements in the area of population dynamics, especially in a spatially-explicit landscape

• Populations that appear relatively safe may suddenly decline if they are subject to threshold responses

• These are when disproportionate pop(n) declines associated with habitat loss


• Good evidence from a wood frog and spotted salamander in ME that as forest cover declines, the ponds occupied by breeding individuals declines drastically as well

• Of course, some patchily distributed sp may look like they have metapop(n) dynamics, but may be temporally disjunct (i.e. early succ sp)

Modeling Approaches

• There are many problems with conservation biology– Triage-based– Lacking information– Lack replicates

• However, agencies want ‘quantitative’ models that predict the fate of populations or can be used to compare different approaches

Modeling ApproachesPopulation Viability Analysis

• PVA examines the demographic effect of different threats or management practices on a pop(n)

• It is essentially a quantitative risk analysis and can compartmentalize various stages (e.g. juv surv, fecundity)

• In most cases, the data required for a sound PVA is relatively large (Essay 12.2)


• There are concerns over the quality of PVA as there can be many assumptions or unknowns

• Brook et al. (2000) conducted retrospective PVAs on 21 long-term data sets from birds and mammals (using first ½ of data)

• Largely accurate (but v. good datasets)


• Habitat-based PVAs can help understand how landscape changes (anthropogenic or natural) can impact the viability of a population

How to Determine Viability

• Population trend data

• Detailed demographic data

• Habitat potentials

Determining Impact

• Develop predictive models that estimates probability of occurrence of target species in suitable habitat.

• Apply models to different plan alternatives.• Translate habitat into population viability.• Predict populations viability over the next 50

years under all alternatives.

Five Hypothetical Management Alternatives

• Simulated CNF under five scenarios– no disturbance– no harvest– expected harvest – 200% (2x expected harvest)– 300% (3x expected harvest)

Predicting Population Viability

• Assume that sufficient habitat is required to support 250 breeding pairs per species.

• Calculate mean territory size from literature.

• Divide high probability habitat units by mean territory size to determine pairs supported.

Acadian Flycatcher

ACFL

0 5 10 15 Ki lometers

N

EW

S

Acadian Flycatcher

suitablehabitat

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

1993 2003 2013 2023 2033 2043 2053

year

hig

h p

rob

. hu

nodist

nocut

expected

200%

300%

MVP

Acadian Flycatcher(4,300 to 9,200 – 13,700 pairs)

Chestnut-sided Warbler

Chestnut-sided

Warbler

suitablehabitat

CSWA

0 5 10 15 Ki lometers

N

EW

S

Chestnut-sided Warbler(400 to 250 – 790 pairs)

0

500

1000

1500

2000

2500

3000

3500

4000

1993 2003 2013 2023 2033 2043 2053

year

hig

h p

rob

. hu

nodist

nocut

expected

200%

300%

MVP

Conclusions from Klaus (1999)

• All species considered (n=6) have viable populations from 1993-2053 in almost all simulations

• Late succession species populations increase as forest matured over time

• Early succession species populations decrease as forest matures

• Some less common early succession species under certain management alternatives may fall below minimum viable population levels as the forest matures over time

Hierarchical Analysis

• Most models of population dynamics project future population sizes based on current pop(n) size and per capita birth and death rates

• Some models attempt to incorporate the causal factors that determine the birth and death rates, which may operate at more than one level in a hierarchy of causation


• For example, sparrow birth and death rates are largely regulated by food supply

• Sparrows live primarily in early successional habitats and the availability may vary on a number of complex factors dramatically


• Thus, local factors can regulate local pop(s) while regional agricultural practices may regulate sparrow abundance at another level

• We could build a habitat-specific demographic model to assess future pop(n) based upon 2 assumptions:

1) Demographics don’t change

2) Fraction of habitat doesn’t change


• There are hierarchical processes affecting pop(s) at different levels

• Changes in habitat availability (and accessibility) determine how much suitable habitat exists for a given species


• Consider a region where individual-level and landscape level factors both matter

• Yellowstone, winter, brucellosis & landscape

Oh yeah, and elk…

http://www.geraldbrimacombe.com/The%20Rockies/Wyoming%20-%20Yellowstone%20NP-%20American%20Bison-winter.jpg

Landscape Models

• Individuals move about the landscape and as such, interconnnectedness is extremely important to all populations

• Since there is variability across the landscape, CB are adopting a landscape perspective when designing management plans and analyzing what factors impact populations

Landscape Models

• Consequently, landscape paradigms are being widely considered and adopted

• E.g. source-sink dynamics, metapopulation dynamics, thresholds effects, regional landuse patterns (in and out of management units)

Landscape Models

• One task of conservation biologists is to identify and quantify suitable habitat

• To do this, a sound understanding of the local and landscape niche is necessary

• Frequently, suitable habitat is found in a relatively ‘unsuitable’ habitat matrix

Landscape Models

• BASP breeds in both older-growth pine and clear-cuts, but not middle aged forests

Suitable habitat in a) 1970 b) 1990 and c) 2010

**Note the spatio-temporal variation in suitable habitat

Landscape Models

• Landscape models can inform conservation efforts

• Only a small portion of each reserve is suitable for bamboo

• Increases ecotourism• Infrastructure demands

increased

Spatially Explicit Pop(n) Models

• One of the primary themes of landscape biology is the importance of subtle landscape aspects (e.g. configuration)

• SEPM incorporate actual locations of individuals in suitable habitat and consider the movement among them

• 3 major elements: a landscape map, some landscape change, pop(n) simulation


• Northern Spotted Owl simulations that vary only on the configuration of suitable habitat

• random


• Suitable habitat in a single large patch


• Clusters of suitable habitat surrounded by marginal habitat


• SEPM have been used to better understand how different water management regimes in the Everglades might affect fish and wading bird pop(s)

• Although field results are qualitatively correct, they cannot predict more than 20-40% of variation in fish density

• Why?

Challenges and Opportunities

• In addition to “simply” trying to assess viability of populations, it is also necessary to project ecological, social, and economic influences that will alter how humans interact across the landscape (remember panda)

• Incorporating alternative-future analysis makes use of several distinct options


• Alternative futures considered and several new conservation and restoration opportunities were identified

Sp and Landscape Conservation Frequently when it comes time to save or manage a species, nations...

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