Outline for the next 2 weeks

Habitat loss, degradation and fragmentationchanges to the landscapeevaluating the impacts

Guest – Species at Risk –Steph Hazlitt (BC)

Guest – Conservation – a Mexican perspective

Edge effectsEcological TrapsGuest – Species at Risk – Dave Toews (Fed.)

SOME TERMINOLOGY

Habitat loss - major change to habitat - all spp adversely affected - timespan for recovery v long

Habitat degradation - change that affects many but not all

species - may be temporary

Habitat transformation/conversion - refers to process of change

How important is habitat loss?

Fig 3.6 text

Habitat loss is the biggest threat to terrestrial threatened species

How much habitat has been lost?

DATA: Millenium ecosystem assessment Fig. 6.1 text

How much habitat has been lost?

DATA: Millenium ecosystem assessment

AQUATIC SYSTEMS

Coral reefs: 20% LOST + 20% DEGRADED

Mangroves: 35% of assessed systems destroyed in last 20yrs

Freshwater: 3-6 X more is stored behind dams and in reservoirs than flows in the world’s rivers

Coral Reef – Degradation

CO2Currently

380ppm - 80 higher than any time in last 420,000 yrsPredicted

500 ppm by end of century---> global temperature increase of 2C

ResponseReef-building coral will be pushed close to their

thermal limit Carbonate levels will drop below those to sustain

coral reef accretion

Increased bleaching/disease/mortality

Huegh-Guldberg et al. 2007 Science 318:1737-1742

Major causes of habitat loss and degradationAgriculture (conversion to crops, livestock)

Extraction (mining, fisheries,forestry)

Development

Fig 6.9 textDATA: Birdlife International

Habitat loss: agriculture

Grasslands, savannas and shrublands-cover 40.5% of earth’s surface-ideal for agriculture and livestock

Dark areas - >30% landscape is cultivated

Habitat loss: deforestation

ForestsGlobal- 50% of pre-agricultural cover lost in 300 yrsTropical - 1990’s Africa lost 8% of its forested area-current loss 100,000 km2 per year

Canada - 10,000 km2 per year

Habitat loss and habitat fragmentation

Fragmentation (process) has two components:1) reduction in habitat amount2) change in habitat configuration

increase in number of patchesdecrease in size of patchesincrease in isolation

Habitat loss with different effects on

Number of patchesMean patch sizeMean isolation

DOES IT MATTER?

coreCORE

EDGE

Patch number and size also changesthe ratio of edge:core habitat

Edge habitat increases with fragmentationLe

ng

th o

f ed

ge

Leng

th o

f ed

ge

% deformationNumber of patches

habitat

matrix

Habitat lossHabitat loss + fragmentation

Number patchesMean patch sizeMean isolation

Habitat loss + fragmentation+ change in habitat quality at edge

Theoretical effects of habitat loss

Eg Jansson and Angelstam 1999

Theoretical effects of fragmentation per se

+ve landscape complementarityvia access to multiple resources

stability of single species dynamicsvia asynchronous disturbances

stability of 2-competitor systems via trade-off in competitive and dispersal ability

temporary refugia

-ve patch size and resource limitationedge effects

What approaches can be taken to disentangle the effects of

habitat loss and fragmentation

ie changes in habitat configuration

Statistical methods to assess effects

Residuals - unexplained variation after controlling for change in patch size or total edge due to loss of habitat

Statistical methods to assess effects

Eg Villard et al 19993 regions in Ontario33 landscapes (2.5kmx2.5km)

Measured% forest covertotal length of edgemean distance to next patch

presence/absence 15 bird spp

Statistical methods to assess effects

Cover - 6 spp Edge - 4 spp Isolation 1 spp

MESSAGE OF PAPERBoth cover and configuration predict presenceResponses are species specificEffects were not characterized by thresholds

Habitat Loss - Fragmentation - what is happening

coreCORE

EDGE

Fragmentation: understanding the process

Edge habitat will be impacted by biotic factors

resource availability will changewithin patch and

outside patches

species interactions will change predation/herbivory/parasitism

Edge habitat is also modified by:

abiotic factors

(wind, water fluxes, solar radiation)

---> change in vegetation structure microclimate ground cover

Eg pacific northwesttree mortality and blowdown is higherhumidity is reducedphysical effects extend >200m into forest

Edges and animal distributions

eg 1 Coastal scrub, CaliforniaMatrix - urban

Increased run-offReduced native spp cover ---> increased abundance Argentine ant reduced native ant diversity

Suarez et al. 1998 Ecol 79 2041-56

Edges and animal distributions

eg 2 and 3Manaus, BrazilReduced overstoryIncreased understoryHigher tempReduced moisture

Wog Wog, AustraliaIncreased tree fallHigher temp

Reduced leaf litter,

Edges have different beetle communites

Edge effects on inverts +ve and -ve

Edges and animal distributions

Edge effects on mammals are often +ve or neutral

Why? Foraging opportunities at edge or adjacent areas + taller vegetation for other needs

Deer Bats Deer mice Martens and Weasels

Edges and animal distributions

Edge effects on Mammals can be –ve

Atlantic rainforestSoutheastern BrazilPrimates are hunted - “bush meat”Hunting extends several km in from edgesHunting major cause of extirpation from small patches

Area-sensitive songbirds

Are more sensitive to the edge:core ratio

0/16 spp breed

6/16 species breed

Edge effects on birds – biotic factorsPredation - early

dataAndren and Angelstam 1988Sweden

Wilcove et al. 1986Eastern North America

Edge effects on birds – biotic factorsParasitism-early data

Gates and Gysel 1978 Ecology 59: 871-83

Nests at edges suffer higher rates of brood parasitism which reduces fledging success

Increasing distance from edge

Take home messages

Habitat loss is a major threat to biodiversity

Habitat loss also leads to fragmentation

Fragmentation influences patch size and configuration

Abiotic/biotic effects modify edges

Statistical and experimental methods can disentangle the effects of loss and fragmentation