Arizona’s wildlife is facing unique and overwhelming threats for the 21st century that can be summed up in three words, human population growth. Maricopa Association of Governments projects an explosion of 17,000 people living cheek to jowl in Arizona by 2050. Already Arizona’s population exceeds 6million.
A large part of the state’s natural environment is projected to be smothered by a huge megalopolis extending from the Mexican border to Flagstaff and Las Vegas. Anyone who has traveled this corridor in the last few years has witnessed the explosive human growth in this portion of the state. Smaller, but no less disastrous to wildlife, human growth will also occur east to west along the I-40 and I-10 corridors.
Besides the obvious destruction of natural environments, by such infrastructure as buildings and urban areas, this unprecedented growth will impact wildlife in numerous and not always obvious ways. For instance, canals carrying the life blood of the cities form impassable barriers or death traps to many species. Crossings for wildlife are often inadequate in number and size.
Some attempts have been made to providepassage for wildlife but the overpasses are too few and too narrow to provide good connectivity across
The changed way we use water has dried up rivers, streams and springs creating stress on wildlife during hot times of the year.
Our roadways continuously kill millions of vertebrates yearly. Smudges of fur are so common on Arizona’s roadways that we don’t even think about them. Over time, with increasing traffic, roadways have also created barriers that most animals can not pass, creating fragmented habitats. This is analogous to a person being restricted to a city, then to their house, then a room in the house, then a closet. Somewhere in that process one will find it difficult to make a living. That is what is happening to Arizona’s wildlife. They are being squeezed into smaller and smaller areas where they can not maintain population viability.
Already Research Branch’s telemetry data from a variety of species show the same picture. Animals come up to roadways, but do not cross.
Of course, some species, such as bighorn sheep and pronghorn, are more sensitive, but even with others, such as deer, traffic volumes in excess of 4 to 10 thousand vehicles/day becomes an almost complete barrier, a moving fence. Just try to get across I-10 on a normal day to see what a crossing animal experiences. The few that are adventurous risk ending up as bloody splotches on the road, thereby eliminating the most adventurous animals from the population. This mortality exacerbates population fragmentation and restricted gene flow, thereby hastening wildlife population declines and even extinctions.
Roads and urban areas aren’t the only factors fragmenting Arizona’s habitats. Railroads also present barriers to wildlife. Many single track railways now move a train every 15 minutes. Double tracking will only exacerbate this “moving fence” barrier to wildlife.
Agriculture has transformed wildlife habitat over large expanses of Arizona. Although some crops provide food for some species, generally agricultural monocultures are not highly productive habitats for native species. In addition, livestock carry diseases that are deadly for some. For instance, domestic goats introduced contagious ecthyma to the desert bighorn sheep population in the Silverbell Mountains recently causing a large die off.
Off highway vehicle use is fun, so much so, that its incidence is exploding. Besides destroying vegetation and wildlife habitat the noise and activity of ATVs has an undoubted, but largely unknown, impact on wildlife.
Even such “passive” activities as hiking and nature walks create disturbance to some species. It is possible to love some species to death simply by getting too close to them too frequently. Some species can habituate to human presence, while others cannot.
Invasive Species tend to follow human activities, usually along roadways where seeds are carried by vehicles, or the outback where seeds are carried by hikers or domestic animals and even through our waterways when unwanted species are spread by boaters.
So Arizona's wildlife is embattled on numerous fronts, not all of them noted above. The question is , what can be done about it?
First, is the recognition that business as usual will not do. We need 21st century answers for 21st century problems. The Arizona Game and Fish Department is tackling these problems on many fronts, not the least important being research. Below are a few examples.
The Department’s award winning research on State Route 260 has revealed several insights into how to safely move large animals across highways. Seventeen bridge structures are proposed for about 13 miles of highway east of Payson. Researchers monitored several of these already built crossing structures using video cameras to find out how animals reacted to then.
They found that several species of wildlife used the underpasses, but the design of the underpasses influenced how much they were used. An underpass with concrete sided walls (West Underpass) was used much less than a nearby one (East Underpass) with natural slopes. Video showed elk standing in the underpass entrance looking up at the top of the concrete wall, apparently looking for lurking predators.
Number of animals recorded on videotape, crossing through underpasses and passage rates by species for six wildlife underpasses, determined from video surveillance 2002-2008, State Route 260, Arizona.
GPS tracking collars showed that elk did not cross highways ubiquitously, but had preferred crossing locations.
Researchers also found that where traffic lanes were widely separated and required two widely separated underpasses with an intervening atrium, those that were in a straight alignment were used more than those that were offset. Presumably this disparity was explained by an approaching animal’s ability to see through the underpasses.
Locations of GPS telemetered elk along Highway 260
Researchers also found that crossing structures were relatively ineffective unless combined with funnel fencing that kept animals from crossing at grade and funneled them to crossing underpasses.
influence of Traffic Levels on Elk - Highway and Wildlife Underpass
One of the most important findings related to traffic volume. The higher the traffic volume the less animals (elk) crossed highways. However, once funnel fences were installed and the animals learned to use them, they were not deterred from crossing the highway safely. Thus two objectives are met by crossing structures with fencing, motorist/wildlife safety and eliminating the barrier effect of the highway to animals.
A similar pattern to elk was shown for white tailed deer. They are much more sensitive to roadway disturbance and tended to avoid crossing SR 260. However, after funnel fences were added to the crossing structures their crossing rate quadrupled.
Besides video monitoring to tell us how effective crossing structures are, the Department is investigating other innovative techniques, such as the automated crosswalk on SR 260. This system detects animals using IR cameras and military grade target acquisition software and then automatically turns on warning signs alerting motorists to animals crossing the roadway ahead
No one knows yet how to get desert bighorn sheep and pronghorn safely across highways, but ADOT in cooperation with the Department, is in the process of building three overpasses (the sheep go over the highway) on US 93, just south of Hoover Dam, which we think will work. Once built these overpasses will be monitored by the Department to see if indeed sheep adapt to them as well as elk did to the underpasses on SR 260. Similar research is being done on pronghorn along Hwy 89 to see if we can find a way to safely move pronghorn across highways.
Simulation of sheep overpass on Highway 93
Bighorn sheep were captured and fitted with GPS
This is not a complete list of the Research the Department is involved in, but it gives you an idea of the innovative approaches we are using to make highways safer for motorists and wildlife.
Besides Research, the Department is heavily involved in identifying areas important to wildlife. Working with several external partners, we produced a statewide map of Linkage Zones, or areas important for linking one large, undisturbed habitat block with another. These Linkage Zones are made available to a host of transportation, land management agency, county, municipal and development planners to ensure green connectivity is included in their gray connectivity plans.
The Department is also engaged in defining areas of high or important areas of species diversity. All of these tools will shortly be available to planners on-line for inclusion in their development plans. Hence, wildlife concerns, that have previously been excluded from development plans, will now beincluded.
With the recent emphasis on alternative energy, Arizona’s solar and wind resources are being investigated for development. While there are environmental advantages to alternative energy sources, there are also impacts to wildlife. The Department is involved with a host of cooperators to ensure that these types of developments have minimal impact to wildlife.
The Department is cooperating and partnering with a wide variety of external customers and publics to ensure that the Department’s mission to conserve, enhance and restore wildlife during the challenging times just ahead is realized.
For more information contact:
Ray Schweinsburg, Ph.D., Arizona Game and Fish Department
5000 W. Carefree Highway Phoenix, AZ 85086-5000
Phone: (623) 236-7251 E-mail: firstname.lastname@example.org