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

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

AREA, ORGANISMS, and RESEARCH QUESTION The present study analyses species richness along an elevational gradient in Nepal Himalayas Seven taxonomic groups including: trees, herbaceous plants, ferns, cryptogams, and fungi WHAT kind of organism has this correspondence, and why?

INDIA TIBET

Cause Effect ? High Biodiversity High human population Many Biological options for exploitation Human settlements Species rich cultural landscapes Obscured

Research question 1 Which organism has a correlation between human population density and species richness along the total elevation gradient organisms with elevation range information No. of Species with info. Main sources of information Polypore fungi151Adhikari, 2000; Authors own unpublished data. Ectomycorrhizal fungi225Adhikari, 2000; Authors own unpublished data. Lichens336Sharma, 1995; Pandey et al., Mosses464Kattel & Adhikari, 1992; Bhuju et al., 2007; Grau et al., Liverworts360Kattel, 2002; Bhuju et al., Grau et al., Ferns293Iwatsuki, 1988; Bhattarai et al., 2004; Bhuju et al., Trees and herbaceous species614 / 3300Hara et al., 1978; Hara & Williams,1979; Hara et al., 1982; Bhattarai & Vetaas, 2006; Vetaas & grytens, 2002 Bhuju et al., 2007.

Elevation Gradient Deciduous Warm temperate- subtropical Forest Ice & rock Alpine Meadows and heath TROPICAL FOREST low high Elevation Evergreen OAK- RHODODENDRON-Forest MontaneBETULAConiferous Forest &…… 1000 m a.s.l. Interpolated species richness

species ….6000 sp sp sp sp n sp n sum of spp INTERPOLATION : ASSUMING ALL SPECIES ARE PRESNET IN ALL 100M INTERVALS BETWEEN LOWER AND UPPER ELEVATION LIMIT This gives total number of species in all different elevation bands from 100 m to 6000 m a.s.l.

Research question 1 Which organism has a correlation between human population density and species richness along the total elevation gradient OrganismSpecies vs. Human Population Polypores fungi ns Mycorrhizal fungi 0.541*** Ferns 0.439*** Trees 0.631*** Liverworts ns Mosses ns Lichens ns Herbs 0.10 ns

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.

Elevation and Human population density: focus outlier

Research Question 2: Which organism has correlation between richness and human population along the populated part of the gradient m a.s.l. organismSpecies richness cor. Human Population Trees 0.81 Mycorrhizal fungi 0.25 Herbaceous species Liverworts Mosses Lichens Polypores fungi Ferns 0.05 ns

r= 0.81 r= r= r= r= r= r= r= ns

Cause effect High biodiversity High human population AREA of elevation zones Species area relationships

Area result outliers

Correlations between log (species richness) and log (area) in km 2 for target taxa between m a.s.l. taxar Mycorrhizal fungi Polypores fungi Ferns Trees 0.55 Liverworts Mosses Lichens herbs

Cause Effect High human population High biodiversity Climate Temperature

Forest and people Forest cover is influenced by human density Forest cover may influence species richness

humna densuty forest density in % M a.s.l.

log-HUMAN-POPULATION DENSITY and log-FOREST-COVER

Cause Effect High human population High biodiversity reduced forest cover Related to Intermediate disturbance hypothesis

More tree richness at low forest cover !

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

Thank you for your attention Lopped oak forest rich in species

Exploit the dominant species This may be done by: Selective logging in a forest Lopping or pollarding of canopy trees Browsing by large mammals

Biodiversity and disturbance species richness Increasing disturbance

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

Disturbance definition Many different definitions Grime: disturbance = reduced or destructed biomass Browsing, Grazing, Fire or other biomass outtake are regarded as disturbance

Biodiversity; biomass and disturbance species richness increasing biomass increasing disturbance