Download Introduction to Landscape ecology and matrix

Introduction to Landscape ecology and matrix
Dr Elias Bizuru
Senior lecturer
National University of Rwanda
Phone: +250 78 857 60 52
Email: [email protected]
ebisous@yahoo fr
[email protected]
Past landscape
Carboniferous period…
Ecologie de la conservation
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Jurassic landscape….
Ecologie de la conservation
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Cretaceous landscape….
Ecologie de la conservation
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Eocene epoch: This is a wetland inhabited by bats,
birds, and primitive frogs. In this day and age, the
top predators
d
are giant
i
ground
d birds
bi d such
h as the
h
Diatrima. Poised at this moment in time, evolution
almost took a turn toward preventing the
development of large mammals due to the dominance
of these birds.
Ecologie de la conservation
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A scene from the Oligocene, 30 million years in the past. Here a Paleomastodon and proto-hippos
enjoy a wallow at the river's edge, unconcerned that their distant descendants will one day spread
across most of the continents and brave the harsh conditions of the Ice Ag e
Ecologie de la conservation
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Miocene epoch
p
in north
America…
Ecologie de la conservation
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Pliocene epoch….
Ecologie de la conservation
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Pleistonece period: Australopithecus appeared…
Ecologie de la conservation
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Plant history….
Ecologie de la conservation
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What is landscape ecology?
• Landscape ecology is the study of structure,
structure
function, and change in a heterogenous land
area composed of interacting ecosystems.
ecosystems
• IIt is
i an interdisciplinary
i
di i li
science
i
d li with
dealing
ih
the interrelationship between human society
and
d our living
li i space.
Principles of Landscape Ecology
• To understand landscape ecology, we have to focus
on some of its important principles: landscape
composition, structure, function, and change.
– Composition
p
involves the ggenetic makeup
p of
populations, identity and abundance of species in
the ecosystem, and the different types of
communities present.
– Structure involves the variety of habitat patches
or ecosystems
t
and
d their
th i patterns—the
tt
th size
i and
d
arrangement of patches, stands, or ecosystems—
including the sequence of pools in a stream,
stream
vertical layering of vegetation.
– Function
involves
climatic,
geological,
hydrological,
y
g , ecological,
g , and evolutionaryy
processes such as seed dispersion or gene flow.
– Change involves the continual state of flux present
in ecosystems.
14
• A landscape consists of three main
components: a matrix, patches, and corridors.
• If we understand these components and their
interrelationships, we can make better
management decisions at the landscape level.
Landscape structure
LLandscapes
d
consist
i t off the
th matrix
t i (the
(th dominant
d i
t
feature), patches, and corridors that connect the
patches.
t h
• The matrix,
matrix the dominant component in the
landscape, is the most extensive and
connected landscape type,
type and it plays the
dominant role in landscape functioning.
• If we try to manage a habitat without
considering the matrix, we will likely fail to
provide what wildlife need in that area.
• The characteristics of matrix structure are the
density of the patches (porosity), boundary
shape, networks, and heterogeneity.
• If an area has been broken up but the patches
are fairly
f i l close
l
t th the
together,
th patches
t h are still
till
dense enough to be useful for animal
movement.
t
However, if you open up a large forested area
by creating small openings, the patches may
not be dense enough to sustain certain kinds
of animals
Patches
• Patches are nonlinear surface areas that differ in
vegetation
and
landscape
from
their
surroundings.
• They are units of land or habitat that are
heterogeneous when compared to the whole.
• Theyy include four different types:
yp
disturbance,,
remnant,
environmental
resource,
and
introduced
• Disturbance patches are either natural or artificial.
They result from various activities,
activities including
agriculture, forestry, urbanization, and weather.
If left alone, a disturbance patch will eventually change
until it combines with the matrix.
• R
Remnant patches
h
result
l when
h
h
humans
alter
l
the
h
landscape in an area and then leave parcels of the old
patches are ggenerallyy more
habitat behind. Remnant p
ecologically stable and persist longer than disturbance
patches.
• Environmental resource patches occur because of an
environmental condition.
• Introduced patches are ones in which people
have brought in nonnative plants or animals
or rearranged native species.
species
Animals
A
i l moving
i from
f
one area to another
h can
also bring in these nonnative elements.
24
Ecosystem Loss and Fragmentation
Frey © AMNH‐CBC
What is Fragmentation?
The end result of
human settlement
and
d resource
extraction in a
landscape is a
patchwork of small,
isolated natural areas
in a sea of developed
land…
Langham © AMNH‐CBC
Gascon et al. 1999
Fragmentation
g
can also be thought
g off
as “a disruption of continuity”
Source: Sterling © AMNH‐C
28
Fragmentation and Spatial Scale: Scale is
I
Important
t t
Fragmentation
ag e a o can
ca occur
occu aat d
differing
e g sca
scales
es and
a d has
as
different impacts at each level
Region
Watershed
Site or Local
Fragmentation at
regional scale
Fragmentation at
ecosystem level
Nyungwe
Fragment Mabayi
Fragment
Rwegura
Fragment
principal
Fragment
Bugarama‐Teza
Main underlying Causes of Fragmentation
• Agriculture
• Urban
p
development
• Logging
• Mining
• Roads
• Hydroelectric dams
• Groundwater
G
d
extraction
Source: Bureau of Land Management/ photo by Robyn Hertz
Loss and Fragmentation Impacts
• Most of the earth’s biomes have experienced
habitat loss
• Extent and rate of loss are hard to quantify!
–
–
–
–
Limited data in some regions
Differences in classification methods
Lack of historical data
Erratic or poor government reporting
Major Biomes and Their Vegetation
• Tundra – no trees, lichens, grasses and shrubs
• Taiga (or Boreal Forest) – coniferous evergreens
• Temperate forests – include evergreens (spruce),
deciduous forests (oaks)
(oaks), mixed forests
forests, and
temperate rain forests (sequoias)
• Tropical
T i l rain
i forests
f
t – greatest
t t amountt off di
diversity
it
in vegetation (vines, orchids, palms)
• Grasslands – grasses, prairie clover
• Deserts – cacti, small bushes
P
R
E
S
E
N
T
D
A
Y
B
I
O
M
E
S
tundra
taiga
taiga
desert
temp.
decd.
forest
desert
grassland
trop.
rain
forest
scrub
forest
temp
rain
forest
desert
Major Terrestrial Biomes
•
•
Geographic distribution of biomes are dependent on temperature,
precipitation, altitude and latitude
Weather patterns dictate the type of plants that will dominate an ecosystem
faculty.southwest.tn.edu/. ../ES%20%20we16.jpg
Natural Fragmentation &
Habitat Heterogeneity
Source: Ansel Adams
for the US
Department
of the Interior 1933‐
1942
Reasons of high diversity in the
ggraet lakes region
g
Distribution of
rainforests
18.000 BC
Distribution of
rainforests
6000 BC
Phytodiversit
y off Africa
f
Human caused fragmentation vs. natural patchiness
Patch Characteristic
Structure
Wildlife habitat
Contrast between patches
Edge effects
Roads & other Human
structures
Human
Natural
Complex
Suitable to
many species
Simple
Not always suitable & to
fewer species
Less
Less intense
Uniquely
occur and
create unique
dangers
High
Higher intensity
Never
Th Process
The
P
off Fragmentation
F
t ti
Example of the Forest Fragmentation
Process
1975
Moist
Forest,
Rondonia
Brazil
Source:
USGS EROS
Data
Center
Example of the Forest Fragmentation Process
1986
Moist Forest,
Rondonia
Brazil
Source:USGS
EROS Data
Center
T h i l TTerms ffor FFragmentation
Technical
t ti P
Process
Perforation ‐ Holes punched in a landscape
Dissection ‐ Initial subdivision of a
continuous landscape
Fragmentation ‐ Breaking up into
smaller parts
Shrinkage ‐ Reduction in size of patches
Attrition ‐ Loss off patches
h
Source: Murphy©AMNH‐CBC
Biological Dimensions of the Fragmentation
Process
All Images: © AMNH‐CBC
“Area‐Sensitive”
Area Sensitive species
Neotropical migrant songbirds
P r o b a b ility o f O c c u r a n c e
Scarlet Tanager
1
0,8
0,6
0,4
0,2
0
0,3
1
3,2
10
32
100
320
1000
3000
( )
Area of forest (ha)
Modified from: Robbins et al. 1989
50
Why Larger Patches usually support more Species?
• More heterogeneity in larger patches
• Large fragments support larger populations
• Smaller fragments
g
support
pp smaller populations
p p
• A smaller p
population
p
increases the likelihood of
local extinctions
Long‐term effects of reduced patch area on
extinction rates
Modified from: Newmark 1996
How Fragmentation reduces Metapopulation
viability
i bilit
• Reduces patch and population
thereby increasing extinction rates
sizes,
• IIncreases inter‐patch
i t
t h distance,
di t
reduces
d
migration rates between patches, reducing
th
the
lik lih d off local
likelihood
l l populations
l ti
sustaining one another
Source and sink populations
• Metapopulations often have a complicated structure
• Some populations often have higher growth rates and
provide migrants that sustain other populations =
sources
• Others cannot sustain themselves and depend on
migrants from elsewhere = sinks
• Be cautious: sometimes the smallest populations
actually have the highest reproductive success and
actually sustain the metapopulation.
Depiction of a metapopulation
Metapopulations and Dispersal
Source: Gibbs
Edge Effects
• Physical
– Microclimate changes in
light temperature,
light,
temperature &
wind
– Humidity ≅ 100m
• Biological
– Exotic Plants and Insects
– Invasive Plants, Insects
and animals
– Bird Density ≅ 100m
• Synergistic
– Fire
– Hunting pressure by
humans and other
predators
Frey©AMNH‐CBC
Edge Effects in Conservation Reserves
Area: 16 sq K
Edge: 16 K
Reserve A
Area: 16 sq K
Edge: 20 K
Reserve B
Area: 16 sq K
Edge: 32 K
Reserve C
Management of Fragmented Landscapes:
Maintaining Biodiversity
•
•
•
•
•
•
Which species are most vulnerable?
Conduct a landscape analysis ‐ where are the big blocks
and
d connections?
i ?
Evaluate the landscape in a regional context
Can planning avoid further fragmentation
fragmentation, ee.g.,
g retain
corridors that increase connectivity of patches?
Minimize edge effects
Remember small fragments
Characteristics of Species
Vulnerable to Fragmentation
• Species with specialized habitat needs
p
with limited dispersal
p
abilities
• Species
• Species with low fecundity
• Species vulnerable to hunting
• Species that are arboreal
• Co‐evolved species
• Ground nesters vulnerable to predators
Identifying Core Regions at the Regional Scale
Source: Ersts ©AMNH‐CBC
Evaluating
fragment isolation
and scoping out
potential
corridors
Source: CERU, University of Pretoria
Evaluatingg Connectivityy at the Regional
g
Scale: The
Proposed Limpopo
Source: CERU, University of Pretoria
Evaluating Riparian Zones as Corridors at the
Local Scale
Frey © AMNH-CBC
Example: The Effect of Implementing a Prohibition
on Riparian Zone Clearing
Source: Courtesy of the USDA Natural Resources Conservation
Service
Conclusions
• FFragmentation
i
i a complex
is
l
process and
d similarly
i il l
evaluating the impacts of fragmentation on different
landscapes and species is complex
• Key issues are the total area, isolation and composition of
patches that remain in a landscape following
fragmentation
• Fragmentation is an issue at many scales from local to
regional,
g
with different impacts
p
at each scale
• Simple land use guidelines can have direct and major
effects on the level of fragmentation in a landscape