Large-scale edge effects in tropical rainforests and their implications for conservation

(1)

LARGE

-

SCALE EDGE EFFECTS IN

TROPICAL RAINFORESTS AND THEIR

IMPLICATIONS FOR CONSERVATION

SUSAN LAURANCE

11

_{, VALERY GOND}

22

_{& GAEL BRIANT}

33

1

_{JAMES COOK UNIVERSITY, CAIRNS;}

22

_{CIRAD, MONTPELLIER;}

3

(2)

Adequate populations _{Maintain Ecosystem Function}

Conservation Assumptions of Protected Areas

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Are protected areas large enough

to withstand external pressures?

Illegal logging

Hunting

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What is happening to rainforest

trees on forest edges?

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Long term studies of

tree communities at

the Biological

Dynamics of Forest

Fragments Project in

the Brazilian Amazon

•

• Major increases in mortality,

_{Major increases in mortality,}

damage, and turnover within

ca. 100 m of edges

•

• Detectable increases in

_{Detectable increases in}

mortality and turnover up to

ca. 300 m of edges

(6)

Increased wood debris

0 2 4 6 8 10 12 100 1000 Y = 10.87 - 2.30 log X R=0.60, P<0.0001 C W D pr oduc ti on ( M g/ ha /y e a r) Distance to edge (m) 0 2 4 6 8 10 12 100 1000 Y = 10.87 - 2.30 log X R=0.60, P<0.0001 C W D pr oduc ti on ( M g/ ha /y e a r) Distance to edge (m)

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Increased

fire incursion

0 5 1 0 1 5

0 1 0 0 0 2 00 0 3 0 0 0 4 00 0

S u rfa c e fire s a t T a ilâ n d ia , B ra z il

Fi re fr equency ( n o ./ c e n tur y ) D is ta n c e to e d g e (m ) Cochrane & Laurance (2002) Journal of Tropical Ecology

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1 2 3 Dry forest area Dense rain forest area

Large

-

scale desiccation of rainforest

trees in fragmented landscapes

74% to 65%

23% to 20%

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Methods

• Tree canopy moisture

measured over dry season

(June – August) ~ 8 years

(2000-2007)

• MODIS satellite images

12 x 8-day composites

examined pa.

• Leaf water canopy content

measured as SIWSI

(Short-wave Infrared Water Stress

Index) using spectral bands 2

(NIR:841-876 nm) & 6

(SWIR:1628-1652)

• Five edge distances

0-500m, 500-1km; 1-2km &

2-5 km

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-0,05 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 1 2 3 4 5 6 7 8 9 10 11 12

juin juillet août SIWSI -0,05 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 1 2 3 4 5 6 7 8 9 10 11 12 juin juillet août

SIWSI

June July August

Dry forests

Edge rainforest Intact rainforest

Results

-

_-

Average dry season canopy

_{Average dry season canopy}

desiccation rates of three forest types

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1) Landscape fragmentation influences

the

spatial extent

_{spatial extent}

of desiccation

-0,07 -0,06 -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ainf adét Δ_SIWSI d

Zone de São Félix

+ + -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ainf adét d Zone nord Δ_SIWSI + + + + -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ΔSIWSI ainf adét Zone sud-ouest d + + + + + Site 1 and 3 edge penetration distance (d) observable desiccation to 1 & 1.5 km from edge; Site 2 up to 2.7 km 65% Forest cover 51% Forest cover 20% Forest cover

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2) Landscape fragmentation influences

the

magnitude

_magnitude

of desiccation

-0,07 -0,06 -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ainf adét Δ_SIWSI d

Zone de São Félix

+ + -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ainf adét d Zone nord ΔSIWSI + + + + -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ΔSIWSI ainf adét Zone sud-ouest d + + + + + -0,07 -0,06 -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ainf adét Δ_SIWSI d

Zone de São Félix

+ + -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ainf adét d Zone nord Δ_SIWSI + + + + -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 ΔSIWSI ainf adét Zone sud-ouest d + + + + + 65% Forest cover 51% Forest cover 20% Forest cover Steepness of the edge‐interior gradient: New edges Sites 1 & 3 had steepest gradients, but after 1 km little change; Old edges Site 2 had lower canopy moisture but the gradient longer and flatter with strong differences evident at 500m‐1km and 1‐2km.

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-0,07 -0,06 -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 d Δ_SIWSI + + + + +

Zone de São Félix

-0,06 -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 Zone sud-ouest d Δ_SIWSI + + + -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 Δ_SIWSI Zone nord + + + + Seuildinexistant -0.10 -0.02 0.02 0.10

assèchement Variations non humidification

-0,07 -0,06 -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 d Δ_SIWSI + + + + +

Zone de São Félix

-0,06 -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 Zone sud-ouest d Δ_SIWSI + + + -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0 1 2 3 4 5 6 7 8 Δ_SIWSI Zone nord + + + + Seuildinexistant -0.10 -0.02 0.02 0.10

assèchement Variations non humidification

3) Landscape fragmentation influences

the

progression

_progression

of desiccation

65% Forest cover 51% Forest cover 20% Forest cover Site 1 & 3 showed increased desiccation distance to 3.7 & 1.8 km Site 2 showed no change – fragments are “saturated” by edge effects No ‘d’ threshold