Biologists and Bushmeat: Modeling the Effects of Road and Trail Building

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Biologists and Bushmeat Modeling the Effects of
Road and Trail Building on Primate Populations in
Yasuní National Park, Ecuador Jonathan Greenberg
and J. Lawrence Dew, University of California at
Davis

• A Virtual Hunter
• We used the GIS modeling package ARC/INFO to
  determine a hunters maximum possible range given
  the following parameters
• Digitized raster maps of the road and trail
  systems we assume that all non-trail and road
  pixels are pristine rainforest.
• Hunters' starting location for this study
  hunters were presumed to start at the most
  prominent trailhead along the road.
• Terrain traverse time researchers familiar with
  the area estimated the average time required to
  cross one meter of the three different terrain
  types road, trail, and uncut forest. Roads
  allowed a 4 km/hr walking speed, trails 1.5
  km/hr, and forest 0.75 km/hr.
• Hunting time while the Huaorani spend
  approximately 8 hours/day hunting (or a 4 hour
  radius given the hunters return to their starting
  point), the computational cost of a complete
  model of this is currently prohibitive. We used
  a 1 hour radius (or a 2 hour hunt) from which
  longer hunt times can be extrapolated.
• The COSTDISTANCE function determines the shortest
  distance from the starting point to each pixel in
  the grid, constrained by hunting time.

The Place Yasuní National Park is located in
eastern Ecuador South of the Napo river. It
encompasses the most biologically diverse
tropical rainforest ever described including a
staggering 350 tree species per hectare, as well
as hundreds of bird species and 11 primate
species in an area of 15,000 km2. The Pompeya
Sur-Iro oil-access road runs from the Napo river
for over 100 km south through the park and the
Huaorani Indigenous Reserve. Ferries connect
this road with towns and markets to the north.

• The Players
• The area is home to four primary groups of
  players
• The Huaorani, a group of hunter-gatherers,
  swidden agriculturalists, and day laborers who
  presently hunt for both sustenance and for
  cash-profit in the National Park.
• Petroleum extractors who carved the Pompeya
  Sur-Iro road in the mid 1990's and who now
  maintain it to access drilling platforms and
  transport personnel and supplies to oil
  refineries within the park.
• The Yasuní Research Station, a scientific
  research station run by the Catholic University
  of Ecuador and housing researchers from UC Davis
  and elsewhere.
• The woolly monkey, Lagothrix lagothricha, an
  easily-shot and slow-reproducing primate which
  fetches a significant price on the bushmeat
  market.

The Low-impact road The Pompeya Sur-Iro road
was touted by the oil company as having a low
impact on the biodiversity of the region. Our
results indicate otherwise. In the area near the
researcher trail system, the oil company built
10.2 hectares of road and researchers built 4.5
hectares of trails. A pristine forest allows a
hunter access to 159 hectares, or approximately
49 woolly monkeys (at 0.31 monkeys/ha.) within
one hours walk (Figure 2). With the increased
forest access provided by the road, a hunter has
access to 446 hectares of forest or 138 woolly
monkeys (Figure 3). By adding the researcher
trail system into the equation, a hunters access
grows to 545 hectares or 169 woolly monkeys
(Figure 4). Following the construction of the
road, the hunters experience a 180 increase in
prey accessibility. The trail system provides an
additional 62 increase in accessibility.

• The Problem
• At the time of the road's construction, little or
  no hunting had occurred in the region for many
  years and monkeys were plentiful and unafraid of
  humans. UCD researchers established a trail
  system along the road to study these animals
  (Figure 1). Huaorani locals have since then
  settled along the road and used the increased
  access the road provides for hunting adjoining
  forests and selling bushmeat in distant markets.
  Woolly monkey populations along the road have
  crashed.
• Here, we hypothesize that a combination of the
  road system and researcher trail systems greatly
  increase hunter's potential access to prey
  animals, putting unguarded animals at risk. We
  use GIS modeling techniques to test this
  hypothesis by comparing the maximum ranges of a
  hunter in three landscapes
• pristine forest prior to the intrusion of the oil
  company.
• forest accessible by road.
• forest with a road and a researchers' trail
  system present.

Avoiding Hunters Our results confirm
mathematically the intuitively apparent effects
that roads and trails can have on hunters' access
to prey. Recent surveys have found drastic
declines in monkey populations along the road,
and communication with researchers elsewhere
indicates that this is far from an isolated
phenomenon. Reserve designers and field
researchers should consider the potential future
impacts of constructing roads and trails. GIS
technology will prove valuable for this task. Our
future research will examine how road and trail
design strategies can minimize accessability. We
will be modelling how the removal of trailheads,
placement of trails in relation to hunter
communities, and the advent of vehicular
transportation can change hunters' ranges. While
long-term field research can correlate strongly
with long-term conservation, habitat disturbance
caused by reserve managers and researchers can
also prove more harmful than helpful if not
followed through with appropriate conservation
measures. Managers and researchers should
consider the ethical responsibilities involved in
cutting trails and surveying undisturbed habitats.