SPECIES AND LANDSCAPE

APPROACHES

TO CONSERVATION

Ecology 6080 - Pringle lecture: 13 October 2009

Determinants of population change

BIDE factors:

Birth, Immigration, Death,Emigration

(age and sex dependent)

Life history characteristics (e.g., age and sex structure of the population)

(a) Density-independent (birth and death not affected by

population density)

(b, c) Density-dependent: Mortality increases with density-b

birth rates or number of offspring decline with density-c

POPULATIONREGULATION

Allee Effect

•Social behavior can play a direct role in regulating some animal populations

•Intermediate to high population densities may be required to stimulate courtship/ breeding activity or to otherwise allow reproduction

Allee et al. 1949

Queen conch suffers from Allee effects in the Exuma Cays, Bahamas

concept of minimum viable population size

Extinction risks for small populations

1. Demographic uncertainty (small populations extinct by chance events)

2. Environmental uncertainty (loss of local population lead to extinction)

3. Catastrophe (can’t recover from large habitat losses)

Environmental uncertainty: the example of Black Stilt shorebirds in

New Zealand

Example of effects of environmental uncertainty on a small population

• Black Stilts are rarest shorebird in world

• Lay eggs in braided rivers of New Zealand

• Increasing frequency of floods is destroying eggs

• Substitute ceramic eggs, replaced with incubated eggs from hatchery

Population dynamics should be

understood as resulting from a

hierarchy of processes

The landscape species approach

to conservation planning,

activities, and actions

The Success of Endangered Species

Recovery and Habitat Conservation Plans

(i.e. under the Endangered Species Act)

is dependent on this

landscape/species approach

Example: Designinga species recoveryprogram for the Whooping Crane

-15 cranes alive in the early 1940s

-Western flock reached 200 by 2004

-Recovery goal for 2020: 3 self-sustaining populations, each with 25 nesting pairs which persist for 10 years

-Eastern flock began in 2001 from 11 chicks bred in captivity

Reintroducing the eastern flock

-eggs hatched in a captive breeding center in Maryland

-transferred to Wisconsin for flight school

Strict protocol for raising chicks

Metapopulation structure affected by source–sink dynamics:

Until recently critical habitat was defined as the places where a

species was most common instead of defining it based on habitat-

specific reproductive success and survivorship

Source population has high reproductive success and

survivorship

How knowledge of metapopulation dynamics can help in species recovery plans Peregrine Falcon breeding pairs in 3 populations

• Populations augmented with captive release and translocation programs

•Solid circles are actual counts•Line is population estimate without augmentation•Only coastal population has benefited,

Population Viability Analysis (PVA)

•Examines the demographic effects of different threats or management practices on a population or set of populations by projecting into the future

•Quantitative risk analysis which often

combines field studies of organisms life histories with simulation modeling

•Important tool in helping to develop habitat conservation plans for endangered species

PVA and predicting the future of the Florida Manatee

-currently around 3000 total

-PVA used for a 1000 yrsimulation to determine probability of persistenceover 750 yrs

-decreasing chances of long-term persistence from random catastrophes or human caused events

Conclusion: Only under constant conditions (no environmental variation),inexistence of catastrophes, or very large population sizes does the manatee population have high chances of surviving in the long term. (Marmontel 1993)

The California Condor Recovery Program

PVA used to determineHabitat Conservation Plan

•1987 - last 27 condors captured from wild and put into captive breeding program

•2006 - 290 birds with 140 in wild

•~$20 million spent since 1980

Goal: 3 separate populations of 150 birds each

Releasing condors into an overall population sink?

• ingestion of lead shot

• power lines

• hunting

Landscape models for Conservation

-Landscape approach recognizes the interconnectedness of populations and incorporates this concept into models and management plans

1970 1990 2010

Note the island-like

nature of the habitats

Distribution of suitable breeding habitat for Bachman’s Sparrow:

Necessity of a landscape approach in developing recovery plans for the Florida Panther

Recovery goals: -3 viable populations of at least 240 individuals have been established and maintained for a minimum of 14 yrs

-sufficient habitat quality quantity and spatial configuration to support these populations is protected

Current status: 30-50 individuals; inbreeding and mortality

Recovery goals (Continued):

-population may be distributed in a metapopulation structure composed of subpopulations that total the appropriate number of individuals.

-There must be an exchange of individuals and gene flow among sub-populations

-For down-listing, exchange of individuals can be either natural or through management (the latter in a formally documented and funded manner)

-For de-listing, exchange of individuals and gene flow among subpopulations lmust be natural (I.e. not manipulated or managed)

-Habitat should be un-fragmented and accommodate hunting, breeding, dispersal and territorial behavior supporting each metapopulation at a density of 2-3 animals/100 mi2

Regional planning:

- use of 20 yrs of radio telemetry data and GIS software to develop a regional blue-print for landscape restoration that enhances dispersal and facilitates colonization

-almost 1 million ha of forest identified in a barrier-rich patchwork of land uses

-this can serve as the basis for future land-use decisions

-large scale land protection must happen quickly

Spatially Explicit Population Models

(SEPM)Composed of three major elements:

(1) a landscape map depicting habitat patches

(2) a scenario for how the landscape will change in the future

(3) a series of population models that include movement traits

Results of a simulation model for Northern Spotted Owls where suitable habitat is scattered

Results of a simulation model for Northern Spotted

Owls where suitable habitat is clustered

Results of a simulation model for Northern Spotted Owls where suitable habitat is clustered and surrounded by marginal habitat

All species aren’t created equal

• Ecologically functional populations (EFP)

(all pollinators, etc)

-Strong interactors (ecological engineers

elephants and beavers)

-Keystone species and resources

(hornbills, fruitbats, fig and palm trees)

Example #1 of strong interactor: Hornbills

• large birds

• disperse large seeds (mostly)

• few disperser substitutes, except certain primates

• Old World tropics

Greater Hornbill in fig tree

Effects of declines in crested black macaques on number of seeds (fruits) produced by tree, Dracontomelon dao .

Effects of declines in disperser populations (hornbills and primate) on numbers of seeds produced by tree, Polyalthiaglauca

Example #2 of a strong interactor:The American Burying Beetle

Plays an important role in nutrient cycling since its life cycle centers on two animal carcasses - one in which it Is born and one which it rears its young

Summary

• Population dynamics should be treated in hierarchical manner

• Populations exist and function in landscapes

• Metapopulation, sources and sinks should be examined

• Functional groups, especially keystone species and resources should be given special attention

Is the world itself sink habitat

for specific species or groups of species

- given environmental factors

operating at regional and global scales?

…..If so - how can this be reversed?

St Lawrence Beluga Whales

Seriously impaired reproductive success - death rate exceeds birth rate

Polar bears:A double whammy

1. Bioaccumulation of POPs and impaired reproduction

2. Global warming, melting of ice sheets and loss of arctic habitat