Congruence between species richness and human population density: reconciliation or conflict?

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Congruence between species richness and human
population density reconciliation or conflict?

• Ole R VETAAS
• Unifob Global, University of Bergen, 5015
  Bergen, Norway,
• M. CHRISTENSEN
• University of Copenhagen, Forest and Landscape,
  Denmark

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Congruence between species richness and human
population density

• Human action is often claimed to be the main
  cause behind habitat loss and biodiversity
  reduction.
• CONTRADICTION to (?)
• Large parts of the globe have enhanced
  biodiversity, and at the same time these areas
  have a high density of people

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AREA , ORGANISMS, and RESEARCH QUESTION

• The present study analyses species richness
  along an elevational gradient IN THE NEPAL
  Himalayas
• Seven taxonomic groups including trees, ferns,
  cryptogams, and fungi
• WHAT kind of organism has this correspondence,
  and why?

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INDIA
TIBET
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Cause Effect
Obscured

• ?
• High Biodiversity High human
  population

Many Biological options for exploitation
Human settlements
Species rich cultural landscapes
Human settlements
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Research question 1 Which organism has a
correlation between human population density and
species richness along the total elevation
gradient
Species with altitude info Main sources of information
Polypore fungi 151 Adhikari, 2000 Authors own unpublished data.
Ectomycorrhizal fungi 225 Adhikari, 2000 Authors own unpublished data.
Lichens 336 Sharma, 1995 Pandey et al., 2002.
Mosses 464 Kattel Adhikari, 1992 Bhuju et al., 2007 Grau et al., 2007.
Liverworts 360 Kattel, 2002 Bhuju et al., 2007.
Ferns 293 Iwatsuki, 1988 Bhattarai et al., 2004 Bhuju et al., 2007.
Trees 614 Hara et al., 1978 Hara Williams,1979 Hara et al., 1982 Bhattarai Vetaas, 2006 Bhuju et al., 2007.
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Elevation Gradient
Interpolated species richness
Montane BETULA Coniferous Forest

Evergreen OAK-RHODODENDRON-Forest
Deciduous Warm temperate-subtropical Forest
1000 m a.s.l.
TROPICAL FOREST
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INTERPOLATION ASSUMING ALL SPECIES ARE PRESNET
IN ALL 100M INTERVALS BETWEEN LOWER AND UPPER
ELEVATION LIMIT
species 100 200 300 400 500 . 6000
sp1 0 0 1 1 0 0
sp2 1 1 1 1 1 0
sp3 0 0 0 1 1 0
sp n-1 0 0 0 0 1 0
sp n 0 0 0 0 0 0
sum of spp 1 1 2 3 3 0
This gives total number of specie in all
different elevation bands from 100 m to 6000 m
a.s.l.
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Research question 1 Which organism has a
correlation between human population density and
species richness along the total elevation
gradient
Organism Species vs. Human Population
Polypores fungi 0.156 ns
Mycorrhizal fungi 0.541
Ferns 0.439
Trees 0.631
Liverworts -0.187 ns
Mosses -0.024 ns
Lichens -0.038 ns
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Scale and patterns

• This large scale pattern may in part be ascribed
  to the fact that very few people live in very
  unproductive species-poor areas, such as deserts,
  sub-arctic-biomes, or high mountains.
• The correspondence between species richness and
  human density may not be evident at shorter
  spatial extents such as along an human populated
  elevation gradient.

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Research Question 2 Which organism has
correlation between richness and human population
along the populated part of the gradient 200 -
3100 m a.s.l.
organism Species/ Human Population
Polypores fungi - 0.62
Mycorrhizal fungi 0.25
Ferns 0.05 ns
Trees 0.81
Liverworts - 0.70
Mosses - 0.58
Lichens - 0.62
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Cause effect

• High biodiversity High human population

AREA of elevation zones Species area
relationships
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Area result
outliers
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Pearson correlation between log (species
richness) of different groups and log (area) in
km 2
Metre above sea level 200-3100
Mycorrhizal fungi - 0.28
Polypores fungi - 0.77
Ferns - 0.53
Trees 0.55
Liverworts - 0.80
Mosses - 0.77
Lichens - 0.79
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Obscured Cause and Effect

• High human population High biodiversity

Climate Environmental
temperature
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Forest and people

• Forest cover is influenced by human density
• Forest cover may influence species richness

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humna densuty
forest density in
M a.s.l.
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log-HUMAN-POPULATION DENSITY and
log-FOREST-COVER
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Obscured Cause and Effect

• High human population High biodiversity

reduced forest
cover Related to Intermediate disturbance
hypothesis
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More tree species at low forest cover !
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conclusion

• Forest cover predicts tree specie richness
• Forest cover is determined by climate at higher
  elevation and human density at lower elevation
• Thus people may have a positive impact on tree
  diversity
• Management implication a moderate reduction of
  total forest cover may enhance richness rather
  than reduce it

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Thank you for your attention
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Biodiversity and disturbance
species richness
Increasing disturbance
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Theory Intermediate disturbance hypothesis

• Hutchnison (1951), Grime (1973b), and Connell
  (1978), has suggested that there is higher chance
  for many species to coexist, when a community or
  landscape is moderately disturbed.
• This tenet is well accepted, although disturbance
  is difficult to define and measure

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Disturbance definition

• Many different definitions
• Grime disturbance reduced or destructed
  biomass
• Browsing, Grazing, Fire or other biomass outtake
  are regarded as disturbance

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Biodiversity biomass and disturbance
species richness
increasing biomass
increasing disturbance
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Exploit the dominant species

• This may be done by
• Selective logging in a forest
• Lopping or pollarding of canopy trees
• Browsing by large mammals