Threats to forests and forest conservation

1
Threats to forests and forest conservation

• Yahner Chapter 6-8

2
Air Pollution Effects on plants
Air Pollution and Forest Decline (Waldsterben)
3
Air Pollution Effects on plants

• Can occur in gaseous or particulate form
• Primary (SO2, NOx, CO) versus secondary (O3,
  photochemical products) forms important
  distinction. Also particulate versus soluble
  distinction.
• Can be toxic to plants (SO2)

4
Forest Decline

• An environmental problem that came to prominence
  in 1980s.
• Symptoms
• 1. Growth decrease
• (slower growth, increase susceptibility to
  pathogens,
• premature aging of needles)
• 2. Abnormal growth
• 3. Water Stress

5
Surveys in Europe show that there has been
substantial damage in many of the forest of Europe
The problem has been particularly prevalent in
Poland, Czech Republic, and a major concern in
many other European countries. It has been a
concern in high elevation Eastern coniferous
forests in the US
6
Hypotheses concerning forest decline

• Poor forest management
• Aging of forests
• Climate change/severe climate
• Nutrient deficiency
• Viruses/pathogens/pests
• Pollution gases, soil acidification (including
  the increase in aluminium, and other ions in
  soil), nitrogen saturation, trace gases,
  pesticides etc.

7
Multiple simultaneously applied stresses may be
the cause.
Nihlgard, proposes the accompanying scheme that
shows a chronological sequence of stress
Although this has retreat from public attention
in recent years the problem has not disappeared -
there are still debates over the appropriate ways
to assess the problem, and about the cause of the
problem, and about the public policy implications
of forest decline
8
10,000 years ago forests covered 6.2 billion
hectares worldwide (45.5 of land surface excl.
Antarctica)30 decline since 10,000 years ago.
Overall there has been a 19 reduction in forest
cover worldwide since 1700
9
Deforestation

• The temporary or permanent clearance of forest
  for agriculture or other purposes
• Grainger (1992)
• Definitions can be important in discussing the
  extend of impact.

10
Deforestation as a world-wide phenomenon dates
back millenia but has been an accelerating
process. Since pre-agriculture total forest
extent has diminished 20. This does not mean
that 80 has never been cut. Only 12 of forest
intact.
The Central European forest has been greatly
diminished in extent and fragmented since 900 AD
11
Deforestation very rapid in the US. More forest
lost in 200 years in the US than in 2000 years in
Europe
12
There have been substantial problems world-wide
in estimating the extent of forest lost - has led
to significant inflation in reported forest loss
Deforestation in tropics has been going on for
millenia - 3000 BP in Africa 7000 BP in the
Americas, 9000 BP in India and New Guinea.
New spasm of tropical forest loss has been very
intense
13
Great variability in estimates of extent of
tropical forest loss. FAO figures are 16.8
million ha in 62 countries in 1990 - up from 9.2
m ha in the 1970s
14
Considerable variation in the rate of loss in
different regions
Great loss of ecosystem function
Philippines, Malaya, Australia, Indonesia,
Vietnam, Bangladesh, Sri Lanka, Central America,
Madagascar, West Africa and Eastern Amazonia are
vulnerable hot spots
15
Possible consequences of tropical forest loss
16
Summary

• Rate of rain forest lost are difficult to measure
  and simple predictions of when the forests will
  be gone are FLAWED!
• Some rain forests are more endangered than others
• History of use is long
• Much uses remain to be discovered (indigenous
  people lost faster than the forest itself)
• Plans for forest conservation need to be
  economically realistic.

17
Loss of Habitat through deforestation and
conversion may lead to extinction. We spent much
of the last class attempting an explanation of
the causes of extinction. The examples are
general but we conclude with a discussion of
fragmentation in forest and with a discussion of
conservation measures.
18
A refresher definition"Biodiversity is the
variety of life and its processes. It includes
the variety of organisms, the genetic differences
among them, the communities and ecosystems in
which they occur, and the ecological and
evolutionary processes that keep them
functioning, yet ever changing and adapting."
Noss and Cooperrider, (1994).
Biodiversity Loss
19
Rates of recent extinctions seem to follow
explosion of human population
20
A Litany of Examples

• One fifth of bird species has been eliminated in
  the past 2 millenia - many of these are island
  populations (11 of those remaining are
  endangered.
• From 1940s to 1980 population densities of
  migratory songbirds has dropped 50 and many
  species are locally extinct
• 20 of worlds freshwater fish are in extinct or
  close to it. Lake Victoria example is a dramatic
  illustration.

21

• Over 200 species of plant in US have become
  extinct, another 680 are threatened or
  endangered.
• In Germany 34 of 10,290 insect species are
  threatened or endangered
• Fungi of Europe are undergoing a mass extinction
  on a local scale - air pollution is the major
  issue here.
• E.O Wilson The Diversity of Life 1992

22
Habitat degradation ranks as primary cause
23
A theoretical digression - what do we know about
extinction?
24
Extinctions Poster Child Raphus cucullatus
(last seen 1662 - if you have information about
the whereabout of this ungainly bird please
contact.
The song of the dodo, if it had one, is forever
unknowable because no human from whom we have
testimony ever took the trouble to sit in the
Mauritian forest and listened David Quammen,
The Song of the Dodo, 1996.
Dodos were hunted for well over half a century
starting with the Portuguese arrival in 1507 -
this is only part of the story. Pigs and monkeys
(crab-eating macaque) were a bigger threat.
25
More excellent summer reading!
1996
26
Since the year 1600 171 species and subspecies of
bird have disappeared. Of this total, 155 species
and subspecies lived and died on islands
(90).Furthermore, the smaller the island the
greater the probability of extinction.
Three generalizationsCarnivore more susceptible
to extinction than large herbivoresLarge
carnivores more susceptible than small
oneHabitat specialists more threatened than
generalists Conclusion Size matters (population
size). Rarity is dangerous
27
Why Big Fierce Animals are Rare
There is an inefficient transfer of energy from
one trophic level to the next - a rough 10 rule
exists
Three generalizationsCarnivore more susceptible
to extinction than large herbivoresLarge
carnivores more susceptible than small
oneHabitat specialists more threatened than
generalists Conclusion Size matters (population
size). Rarity is dangerous
28
Ecologys most robust generalization species
diversity and area are related
The species area curve ScAz Diversity
constant (for taxonomic group) x Area to the
power of another constant relating to the type of
island.
29
Why does population size matter?

• Accidents
• Drowning, volcanoes, genetic drift, etc.
• Population interactions
• Extinction is simply limitation of population
  density carried to the extreme (Stanley 1979)
• Low population density make the probability of
  extinction high

30
The species-area curve comes to the mainland
Since fragmentation of habitat creates islands
of diminishing size, the prediction from theory
is that diversity will fall - rare species will
fall from the mix
31
Forest Fragmentation
Forest fragmentation results when a large mature
forest is converted into one or more smaller
parts by human uses - agricululture,
urbanization, timber harvesting etc.
Results in islands of forest. In recent years
theories developed for true oceanic islands (esp.
island biogeography) have been applied to these
habitat islands
32
Fragmentation will be expected to result in a
lower species. Why? Isolated islands will be
expected to have an even lower diversity than
less isolated ones.
Continental islands differ from oceanic
ones Age Oceanic islands surrounded by water!
33
Fragmentation has been long a part of Temperate
Deciduous forest. Began in EDF in 1600s and
reached a peak in late 19th C and early 20th
C. Reduction of US forest in lower 48 from 400
million hectares to 188 million ha in early 20th
C. 95-97 of old growth forest is gone from lower
48. Many forested areas of the East US have
become green islands
34
Response to fragmentation variable. E.g. Some
bird species thrive on fragmentation - (edge
species). Conversely species that nest away from
the edge (forest interior) show a negative
response to fragmentation.
35
Why the variable response?

• Some species require more food than is provided
  in a small habitat - large vertebrates for
  example (Florida panther a victim of
  fragmentation).
• Fragments may be too small for breeding
  territories for some birds. With the
  fragmentation of habitat the sites become less
  heterogenous (may not have a stream, for example).

36
Fragmentation and changes in Microclimates

• Fragmentation can have profound effects on the
  physical environments of the fragment.
• More solar radiation flux is experienced is area
  once canopy is removed.
• Temperatures are higher, moisture is reduced
  along the edges.
• Vegetation can respond to this change.
• Fragmentation may encourage the encroachment of
  invasive species.
• Wind patterns change, hydrological changes.

37
How big is big enough?

• Depends upon species
• Greater Yellowstone Area (Yellowstone, Grand
  Teton, plus 5 others) is large enough at 23,000
  sq. miles theoretically for only 6 male
  grizzlies!
• South East Deciduous forest habitat may be too
  fragmented to sustain viable populations of black
  bear long into the future.

38
One proposed land management solution to
fragmentation is the creation of wildlife
corridors. Aids dispersal, re-colonization of
metapopulations. Little known yet about
requirements for effective corridors. For.small
mammals corridors with meters wide with shrubby
vegetation is more effective than hedgerows.
Florida panther
For larger mammals they may need to be as wide as
the typical wildlife home range! 2 km for
white-tail deer. Different criteria depending on
species
39
Corridors

• May increase connectivity of metapopulations
• Corridors may conversely increase the spread of
  noxious weeds.
• Benefits seen by most as outweighing negatives

40

• Edges - a related concept
• Inherent vs Induced
• As fragmentation increase edge increases -
  reduced functional interior.
• Edge effect has often been seen as a positive for
  wildlife - but this depends upon the species.
• Coyotes, red fox, white tailed deer are favored
  by edge

41
Summary

• Habitat destruction, degradation, and exotic
  species are the greatest cause of modern species
  extinction.
• Two areas of habitat that differ only in the size
  of the area will have differences in the number
  of species they support.
• Fragmentation creates island of habitat and is
  usually accompanied by loss of diversity.
• Using our knowledge of natural systems we can
  design better preserves