LAA • 6521 Professor Juan Antonio Bueno Florida International University School of Architecture Tropical Landscapes Road Ecology Further study References LAA • 6521 module 10 Forman, Road Ecology Road ecology Transportation systems have inherently dichotomous characteristics. Roadways and railways provide access to nature, farmland, and urban land. But they also cause considerable ecological damage to the landscape: air pollution, water contamination, soil depletion, and wildlife habitat loss and fragmentation. Principles of road ecology afford the knowledge and applicability to minimize and mitigate the negative impact. Road ecology integrates an array of disciplines and professions through ecology and landscape ecology. Road ecology addresses the sustainability of nature as well as the accommodation of vehicles. Transportation and road ecology must be integrated into urban regional planning, design, and management. Roads act barriers and fragmenters across the landscape. But roadsides can function as habitats for wildlife. Ecologically sensitive planning, design, and management principles from environmental design and engineering include: grading cutbanks and fillslopes to reduce erosion, avoiding severe compaction alongside roads, establishing variety in the adjacent microrelief, and diminishing the release of chemicals into the air, water, and soil. Roadside planting design and maintenance should emphasize: planting of native plant species, eradication of non-native invasive vegetation, incorporation of vegetation resistant to air pollutants and water contaminants, reduction of the need for mowing of grasses, elimination of or at least reduction of the use of fertilizers, herbicides, and insecticides. Overall, roadside design should enhance wildlife diversity and societal interactions in the urban, rural, and natural landscapes. Major effects of roads on the fauna include road mortality as well as habitat loss and separation. Road mortality tends to be highest among highly mobile and generalist animals that require multiple resources and are attracted to roads. Habitat loss most severely affects core-habitat species. Effects are exacerbated if the species have low reproductive rates, low population densities, extensive habitat requirements. characteristics principles design strategies planting design fauna Forman, Road Ecology Avoidance, mitigation, and compensation strategies The ecological impact of roads can be minimized by avoidance, mitigation, and compensation strategies. Avoidance can include tunneling the road, changing the route, and eliminating the road. Mitigation can comprise cleaner fuels, noise reduction berms, wildlife overpasses and underpasses. Compensation encompasses ecological improvement, offsite but in the proximity of the impact, related to habitat quality, extent, and connectivity to offset the detrimental effect that cannot be avoided or mitigated. As ro ...

1. LAA • 6521
Professor Juan Antonio Bueno
Florida International University
School of Architecture
Tropical
Landscapes
Road Ecology
Further study
References
LAA • 6521
module 10
Forman, Road Ecology
Road ecology
Transportation systems have inherently dichotomous
characteristics.
Roadways and railways provide access to nature, farmland, and
urban land.
But they also cause considerable ecological damage to the
landscape:

2. air pollution, water contamination, soil depletion, and wildlife
habitat loss and fragmentation.
Principles of road ecology afford the knowledge and
applicability to minimize and mitigate the negative impact.
Road ecology integrates an array of disciplines and professions
through ecology and landscape ecology.
Road ecology addresses the sustainability of nature as well as
the accommodation of vehicles.
Transportation and road ecology must be integrated into urban
regional planning, design, and management.
Roads act barriers and fragmenters across the landscape.
But roadsides can function as habitats for wildlife.
Ecologically sensitive planning, design, and management
principles from environmental design and engineering include:
grading cutbanks and fillslopes to reduce erosion,
avoiding severe compaction alongside roads,
establishing variety in the adjacent microrelief,
and diminishing the release of chemicals into the air, water,
and soil.
Roadside planting design and maintenance should emphasize:
planting of native plant species,
eradication of non-native invasive vegetation,
incorporation of vegetation resistant to air pollutants and
water contaminants,
reduction of the need for mowing of grasses,
elimination of or at least reduction of the use of fertilizers,
herbicides, and insecticides.
Overall, roadside design should enhance wildlife diversity and
societal interactions in the urban, rural, and natural landscapes.
Major effects of roads on the fauna include road mortality as
well as habitat loss and separation.

3. Road mortality tends to be highest among highly mobile and
generalist animals
that require multiple resources and are attracted to roads.
Habitat loss most severely affects core-habitat species.
Effects are exacerbated if the species have low reproductive
rates, low population densities, extensive habitat requirements.
characteristics
principles
design strategies
planting design
fauna
Forman, Road Ecology
Avoidance, mitigation, and compensation strategies
The ecological impact of roads can be minimized by avoidance,
mitigation, and compensation strategies.
Avoidance can include tunneling the road, changing the route,
and eliminating the road.
Mitigation can comprise cleaner fuels, noise reduction berms,
wildlife overpasses and underpasses.
Compensation encompasses ecological improvement, offsite but
in the proximity of the impact,
related to habitat quality, extent, and connectivity to offset the
detrimental effect that cannot be avoided or mitigated.
As road density increases, death rates increase, and birth and

4. survival rates decrease for the wildlife.
However, faunal mortality can be reduced with the installation
of wildlife structures, crossing passages, and escape structures.
But mitigation passages must accommodate sufficient wildlife
usage frequency to at least ensure
genetic variation in a population, but preferably higher
frequencies to maintain population sizes and reduce extinctions.
Roadside design should maximize motorist safety and minimize
installation and maintenance cost.
Roadside design should enhance wildlife movement and create
barriers for the reduction of accidents and fatalities.
Roadside design should incorporate green bridges and tunnels as
channels for water.
Roadside design should incorporate green bridges and tunnels
for seasonal reproductive migrations of crabs, amphibians.
For example—green bridges and wildlife structures as around
Barcelona.
For example—green tunnels and wildlife structures as along
Alligator Alley.
strategies
faunal mortality
design strategies
South Florida, Big Cypress Swamp.
I-75 (Alligator Alley).
Green underpasses (under roads),
green bridges with culverts (across canals),
barrier fences (between road lanes

5. and along canal/right-a-way lines)
South Florida, Big Cypress Swamp.
I-75 (Alligator Alley).
Barrier fence (left center, among trees)
Everglades, Shark River Slough.
Green underpass with culvert
across loop road (center)
Forman, Road Ecology
Roads and water
Roads can disrupt the flow of water, change its physical
characteristics, and alter its chemical composition
in ways that can significantly alter ecological processes in the
landscape.
Sometimes these alterations can approximate natural
disturbances and regenerations.
But more often than not, the changes can be substantially
detrimental.
Water can flood roads, destabilize roadbeds, cause erosion and
landslides, and destroy bridges and other
infrastructure.
Ground susceptible to erosion should be stabilized by planting
vegetation and installing control fabrics
to reduce the rainfall effects of raindrop splash and sheet
erosion.

6. Vegetation diminishes raindrop impact and runoff rate.
Vegetation roots afford coherence to the soil.
Vegetation augments water infiltration and evapotranspiration.
Vegetation filters pollutants and sediments from the soil.
Where sheet flow becomes channelized into rills and gullies, it
is necessary to perform
ground stabilization and water diversion for prevention as well
as soil tillage for necessary repairs.
Beyond the prevention of erosion, on-site runoff and sediment
should be managed in situ.
Ground surface exposure should be limited,
sediment should be retained on site by filtering low-flow run-
off with structural control measures,
and off-site runoff should be prevented from entering site.
Temporary and permanent seeding may also be appropriate in
areas with potential for low levels of erosion.
On uplands along river watersheds, the emphasis of road design,
construction, and management should be the
prevention of surface water and groundwater contamination,
since it may affect the headwaters of streams & the aquifers.
On hillsides, the focus should be on the control of water to
avert contaminants from entering streams,
and to prevent washouts and landslides with routing structures
and drainage systems.
On lowlands, the emphasis should be on the conduction of water
to prevent road flooding and washouts,
and containment of pollutants to prevent contamination of
groundwater and surface water.
water flow
erosion

7. benefits
design strategies
Forman, Road Ecology
Chemical pollutants
Chemical pollutants from roads and vehicles scatter through the
air, and run off the road and seep into the ground
with the rainfall to accumulate in the soil, plants, and animals
to the detriment of ecological systems.
For example—vehicles may be sources of pollutants in the form
of
organic compounds (hydrocarbons), mineral nutrients
(nitrogen and phosphorus), and heavy metals (zinc and
cadmium).
These pollutants can cause smog, eutrophicate aquatic habitats,
and sicken animals and humans.
Greenhouse gases, including and carbon dioxide from fuel
combustion, accumulate in the stratosphere,
causing global warming, higher sea levels, and extreme
weather events.
Ozone and nitrogen oxides from vehicular exhausts accumulate
in the troposphere and negatively affect vegetation.
Pollution particles and aerosols accumulate locally, regionally,
and globally.
Pollutants should be contained at the source through structural
practices,
such as environmental planning, integrated pest management,

8. and bridge maintenance.
The effects of pollutants should be mitigated by structural
practices,
such as porous pavements, sand filters, infiltration trenches,
grass swales, detention wetlands, and retention ponds.
pollutants
greenhouse gases
design strategies
Forman, Road Ecology
Wetlands and roads
Where wetlands are unavoidably impacted by roads and vehicles
in a negative way,
ecological on-site mitigation or off-site compensation,
including mitigation banks and donor-wetland projects,
need to be considered and implemented.
However, replication and reintegration within the landscape,
especially hydrology,
are of paramount importance for landscape ecological success.
Replication and reintegration within the landscape include
the species structure, ecological function, and seasonal
changes of the original wetlands.
In addition, not just the total area, but also the separate size,
number, shape, and connectivity
of the original landscape elements need to be replicated.
wetlands

9. design strategies
Forman, Road Ecology
River and road networks
River and road networks often align along riparian corridors,
and intersect at bridges and culverts,
where the interactions may greatly affect the ecology of the
streams.
The effects may be near the contacts and intersections
or may also extend along the stream, and to the floodplain and
the riparian forests.
Along rivers, roads should be aligned as to accommodate ample
upland corridors for animal movements.
At crossings, culverts and bridge approaches can impede animal
movement, obstruct stream flows,
and cause downstream sedimentation.
To counteract these effects, culverts should approximate, as
much as possible, the existing river conditions.
including the natural stream depth, slope, velocity, and
substrate.
Culvert heights twice water depths as well as stream velocities
of 0.5 meter per second are suitable for warm-water fish.
In the case of tidal marshes and swamps, the estuarine
connectivity and the tidal ebb and flow should not be
obstructed.
A typical remedy for existing conditions is increases in culvert
size and quantity to increase the flow.
Tidal creeks with salt ponds or freshwater lenses over saline

10. groundwater may also be created
to increase flow and provide wildlife habitat during low tides
and dry seasons.
effects
design strategies
Culvert types (optimum, top)
Forman, Road Ecology
Windbreaks and roads
Windbreaks, such as hedgerows and forest strips, can be used to
modify horizontal wind speed, turbulence,
and vortex airflows over roads and roadsides.
To a significant measure, their height and porosity can
determine the resultant effect.
In general, porosity controls wind speed, and height determines
the effectual horizontal effect.
Porous windbreaks reduce turbulence, but decrease windspeed
only slightly over a long distance.
Conversely, dense and solid windbreaks considerably augment
upwind and downwind turbulence,
but decrease windspeed significantly over a short distance.
Often, moderately porous windbreaks may optimize the effects.
Vegetation windbreaks contribute to the fertility of the soil,
while also averting the loss of fertility that is caused by the
wind erosion of fine particles rich in nutrients from the soil.

11. Wind erosion can be diminished by the reduction of open field
size along the predominant wind direction.
windbreaks
design strategies
soil fertility
wind erosion
Further study
Richard T. T. Forman et alii, aliae
Road Ecology: Science and
Solution
s
Washington, DC: Island Press
References
Richard T. T. Forman. 1995
Land Mosaics:

12. The Ecology of Landscapes and Regions
Cambridge: Cambridge University Press
Richard T. T. Forman. 2004
Mosaico territorial para la región
metropolitana de Barcelona.
Barcelona: Editorial Gustavo Gili
Richard T. T. Forman et alii, aliae
Road Ecology: Science and