<h2>Flies as bioindicators of grazing pressures in Mongolia</h2>
Faculty Mentor: C. Riley Nelson, Department of Biology
For over fifty thousand years, humans have affected their surrounding environments in
a negative way. As the human population continues to increase, concerns about
extinction and other human-influenced problems including climate change, habitat
degradation, pollution and introduction of invasive species are becoming more and
more difficult to ignore (Oreskes, 2004). Mongolia, with its low population density and
richly diverse biogeographical landscape, has retained much of the biota that has been
lost in surrounding more populous Asian countries. Much of the fauna is relatively
unknown. A growing concern in Mongolia is the commercialization of grazing. Although
grazing has been an integral part of the nomadic culture in Mongolia for centuries, the
increased cost of cashmere has led to more grazing in more places, leaving many
previously pristine landscapes scathed (Altanbagana & Chuluum 2010).
Because Mongolia is a developing country, scientists there need an inexpensive
method of evaluating land and grazing practices in the future. Yellow pan traps are an
effective, low-effort, high-yield tool for getting an overview of the riparian fly diversity.
Through this project, we used yellow pan traps to identify fly families that are likely
bioindicators, or taxa whose presence indicate a balanced, healthy habitat and are most
negatively affected by grazing (Rainio & Niemela, 2003). As grazing in Mongolia
becomes more prevalent, it is important to measure and monitor the effect it has on the
ecosystem as a whole.
We gathered data using yellow pan traps in a thorough survey of the riparian zones of
the Altai and Hangai Mountains to form conclusions about the effect of grazing on insect
populations and diversity. Plastic yellow bowls were placed evenly across a riverbed at
132 sites over a four-year span in Northern Mongolia (Figure 1). Sites were selected
based on habitat diversity and road accessibility, and we visited about 2-3 sites per day.
Each site was given a grazing rank on a scale from 0 to 4 based on grass length and
presence of native plant communities. At each site, we filled yellow pans with water and
a surfactant, thus trapping insects attracted to the bright yellow color. After one hour,
specimens from each pan trap were collected into vials with 70% alcohol for later
sorting. Flies from each vial were counted and sorted to the family level.
We collected over 18,000 flies (Table 1), from 47 different families, in addition to several
other orders of arthropods. Families most often collected were Chironomidae (5819
from 100 sites), Dolichopodidae (2118 from 94 sites), Ephydridae (2030 from 98 sites),
Muscidae (1780 from 89 sites), Anthomyiidae (668 from 75 sites), Chloropidae (589
from 78 sites), and Phoridae (584 from 51 sites). There was no significant difference
between the number of fly families collected in areas with low grazing compared to the
number of families collected in areas with medium grazing, but there were significantly
fewer families in areas with very high grazing (Figure 2). There was also a noticeable
difference in the composition of the flies collected. For example, in areas with the
highest amount of grazing, more than one third of the individuals were from Phoridae, a
family often associated with fecal matter. In less grazed areas, Dolichopodidae and
Chironomidae were more prominent. Five families collected only in levels with low
grazing were Conopidae, Lonchopteridae, Opomyzidae, Sciomyzidae and Therevidae.
Our results indicate that low fly diversity in general can be used to indicate very high
amounts of grazing. An abundance of the family Phoridae indicates high grazing as
well. An abundance of Chironomidae and Dolichopodidae indicates medium or low
grazing. Conopidae, Lonchopteridae, Opomyzidae, Sciomyzidae and Therevidae are
In conclusion, yellow pan traps are an effective way to have a gauge the biodiversity of
flies in the grassland steppe regions of Mongolia. Because of their low cost and high
yield, they are an effective tool to help locals understand and protect the biota in their
own country. High levels of grazing are having a negative impact on fly diversity.
Altanbagana M, Chuluun T (2010) Vulnerability assessment of Mongolian social–
ecological systems. In: 4th international and national workshop on applications of geoinformatics
for natural resource and environment, Ulaanbaatar, Mongolia, pp 1–11
Oreskes, Naomi. 2004. “The Scientific Consensus on Climate Change.” Science
306(5702): 1686 LP – 1686.
Rainio, J., & Niemela, J. (2003). Ground beetles (Coleoptera : Carabidae) as
bioindicators. Biodiversity and Conservation, 12(3), 487–506.