Transcript Document

Impact of Human Activity on Birds
Observed at Two Arroyos
SEE-U 2001, Biosphere 2
Professor James Danoff-Burg
Professor Tim Kittel
T.A. Erika Geiger
Student: Lily Liew
INTRODUCTION
PRIMARY QUESTIONS
•Does human activity impact the abundance and
richness of animal species?
•If so, how does it affect the abundance and richness?
•If not, what factors other than human activity could
impact the abundance and richness of animal species?
Above: Site One, High Disturbance Arroyo
HYPOTHESIS
•As human activity increases, animal species abundance and richness decrease.
CONTEXT OF STUDY
•Become better informed how lessen adverse impact of humans
•Apply knowledge to responsible land use planning and minimize loss of animal species
METHODS
•Two arroyos selected on campus.
•Arroyos are riparian communities with high biodiversity; ideal to contrast high
impact vs. low impact human activity
• 2 Arroyos located elevation of 1150 meters, 32.6°N latitude, 110.9°W longitude
•High impact arroyo
•Distance to road 19 m to 76 m
•Near housing and insectory; ornamental vegetation; less dense growth
•Low impact arroyo
•Distance to road 425 m to 535 m
•Denser vegetation, less open space
•Data collected over 8 mornings (2 dropped b/c monsoon), bet. 04:45-06:45 hours
•Summarized on Excel
•Analyzed on non-parametric tests (Mann-Whitney Test and Kruskal-Wallis Test)
METHODS (CONT’D)
Summary
1) 3 sites selected at each arroyo, total of 6 sites:
– high impact arroyo--site 1 behind student houses (Arroyos #14 and #15); site 2 opposite
student union building; site 3 next to the insectory.
– low impact arroyo—all 3 sites parallel to the barb wire fencing
2) Measured 24 meter by 15 meter area for each site
3)
Binoculars and bird guidebook used to observe birds for 1.5 hours between 04:45 to 06:45 hours
4) Trees counted within the 24 meter by 15 meter area of each site
Map of Sites
Topographical map of six sites along both
arroyos (A=high impact; B=low impact)
RESULTS
High Impact Arroyo
• More species and individuals observed at high impact arroyo (see Fig. 1)
•At each site, average of 9.7 bird species and 21.3 individual birds were observed (see Fig.
( Site 3,2).
High impact arroyo)
•As distance from human activity increased, number of individual birds and species richness
decreased (see Fig. 3).
Low Impact Arroyo
•Fewer species and individuals observed at low impact arroyo (see Fig. 1)
•At each site, average of 6 bird species and 9.7 indivudals were observed (see Fig. 2)
•As distance from human activity increased, number of individual birds and species richness
decreased (see Fig. 3).
•Species abundance was not significantly different between the two arroyos (Mann-Whitney Test,
Z 1,4= -1.528, P=0.127).
•Low disturbance arroyo had a significantly lower species richness than the high disturbance
arroyo (Mann-Whitney Test, Z 1,4= -2.087, P=0.037).
•Site three from the high impact arroyo did not differ significantly from three sites at the low
impact arroyo (Kruskal-Wallis Test, Chi-Square 1,3=0.392 number species of birds; Chi-square
1,3=0.392 number individual birds). These four sites similar in vegetation and tree density;
fewer species and individuals than first two sites at high impact arroyo
Figure 1: Sites 1 to 3 are high impact sites and sites 4 to 6 are low impact sites. Sites 1 and 2 had a
significantly higher number of bird species than sites 3 to 6.
Total Number of Species and Number of Individuals
Total num ber bird species and individual birds
35
30
25
20
#spp birds
#indiv birds
15
10
5
0
1
2
High Im pact Sites
3
4
5
Low Im pact Sites
6
Figure 2: High Impact sites had higher average number of species and abundance than low impact sites;
there was greater variation from the average value for individual birds than for individual species for both low
impact and high impact sites. Error bars indicate standard average (standard deviation/square root of n samples)
Average Num ber Species of Birds and Average Num ber of Individual Birds
30
25
Average Num ber
20
Avg # species of birds
15
Avg #indiv birds
10
5
0
High Impact Sites
Low impact Sites
Figure 3: As distance from road increases, number of species and number of individuals decreases
Number of Species and Number of individuals vs. Distance to Road
# of species/individuals
35
30
25
# Speci es of bi r ds
20
# of i ndi vi dual bi r ds
Li near (# Speci es of
15
bi r ds)
Li near (# of i ndi vi dual
bi r ds)
10
5
0
0
1 00
200
300
400
500
Distance to Road
600
700
800
DISCUSSION
• Unexpected
results: fewer birds seen at the low
disturbance arroyo than at the high disturbance arroyo.
•Human activity can increase rather than decrease bird
species richness and abundance, eg. in suburban areas
(Blair, 1996)
Site One, Low Disturbance Arroyo
•Certain levels of disturbance can be optimal for species
diversity (Jullien et al., 1996).
•This study did not consider the level of human impact at
each arroyo.
•Other factors that could influence results:
•Construction noise at low impact arroyo could affect number of birds observed
•More mesquite trees at low impact arroyo=more camouflage; harder to see birds
•Birds at low impact arroyo may be more wary
DISCUSSION (Cont’d)
•“Urban exploiters” and “suburban adaptables” adapt well to urbanization, unlike “urban
avoiders; birds at high impact arroyo could be “suburban adaptables”
•Moderate development leads to an increase in ornamental vegetation, water sources, primary
productivity and amount of edge between habitats; benefit species adaptable to human activity.
•Species richness optimal at intermediate levels of disturbance; beyond levels, species richness
starts declining as forest fragmentation increases, and forest patches become smaller and more
isolated (Jullien and Thiollay 1996). More cleared ground at high impact arroyo: more space for
flight; also food left out by humans
•Third site at high disturbance arroyo similar to three sites in the low disturbance arroyo; all four
sites have denser growth, less space for the birds to fly around in, not easily seen
• Species abundance not statistically significant. Need additional sites each arroyo.
•Possible errors include not enough sampling points, misidentification of species. More data
would have to be collected, more sites should be added to each arroyo, and more observations
CONCLUSION
•Human impact can result in significantly higher species richness than low impact.
•Human impact can increase species richness and abundance to an optimal level beyond which it
starts to decline (Jullien et al, 1996); intermediate impact level appears optimal
•Increase in species richness has been linked to moderate development which leaves sufficient
patches of native land and vegetation for animal species to use, and yet provides improved
resources
•High impact arroyo in this study could be classified as a moderate impact
•Species richness could be influenced not only by human factors, but also by native vegetation
growth and size of native land patches
• Low impact arroyo in this study had more dense vegetation not favoured by some birds
•Land use planning could examine what types of animal species would be most affected by
human activity, and plan accordingly to minimize the negative impact of human activity and
preserve native habitats required by certain animal species (Blair, 1996; Recher and Serventy,
1991).
REFERENCES
Blair, Robert B. 1996. Land use and avian species diversity along an urban gradient.
Ecological Applications 6(2):506-519.
Gill, Jennifer A., W. J. Sutherland, A. R. Watkinson. 1996. A method to quantify the effects
of human disturbance on animal populations. Journal of Applied Ecology 33(4):786792.
Jullien, Mathilde and Jean-Marc Thiollay. 1996. Effects of rain forest disturbance and
fragmentation: comparative changes of the raptor community along natural and humanmade gradients in French Guiana.” Journal of Biogeography 23(1):7-2 .
Peterson, Roger Tory. 1961. A field guide to Western birds. 2nd Edition. Houghton Mifflin
Company, Boston.
Phillips, Steven J. and P. W. Comus, eds. 2000. A Natural History of the Sonoran Desert.
Arizona-Sonora Desert Museum Press, Tucson. p.8.
Recher, H.F. and D.L. Serventy. 1991. “Long term changes in the relative abundance of
birds in Kings Park, Perth, Western Australia.” Conservation Biology 5(1):90-102.
Warkentin, Ian G., R. Greenberg, and J.S. Ortiz. 1995. “Songbird use of gallery woodlands
in recently cleared and older settled landscapes of the Selva Lacandora, Chiapas,
Mexico.” Conservation Biology 9(5):1095-1106.
Acknowledgements
Many thanks to all the instructors for
their assistance!