How do roads facilitate economic and social development
- Market access for timber & agricultural products
- Access to remote areas
- Lower costs of land clearing
- Cheap labour
By 2050, how much new road construction is expected, and where will most of it occur?
- 25 million km of new roads are expected by 2050.
- This represents a 60% increase in the total road length compared to 2010.
- 90% of the new road construction will take place in developing nations.
What are the Ecological effects of roads
- Habitat loss
- Road mortality
- Edge effects
- Barrier effects and fragmentation
Describe habitat loss to roads
- The initial and most obvious impact of roads/powerlines
- Road/powerline networks may alter / destroy scarce natural habitats
- Roads create deforestation (example in the Amazon where this increased fire risk)
Give a satistic to show habitat loss from roads
In the Brazillian Amazon:
- Road network has doubled
- >95% of deforestation is within 50km of a road
What species are susceptible to road mortality?
give examples
- Species attracted to roads/roadsides e.g reptiles, herbivores and frugivores, carrion feeders & predators, amphibians (most effected)
- Species with nearby habitat - wetland, grassy verges, fruit
- Species with large- area requirements
- Significant pop. sinks for rare and endangered species
E.g Florida panther: 4-5 roadkills per year from ~75 individuals
What are edge effects from roads?
Roads cause physical, chemical, structural, environmental and biological impacts on the adjacent habitat
How do roads cause pollution
- Chemical emissions = pollution of air, soil and water adjacent to roads
- Energy emissions in the form of noise, light, vibration and movements = disturb wildlife
How do roads cause habitat decay?
- Changing microclimatic conditions: humidity, light, temp, wind speed and turbulence
- Increased tree damage and death
- Increased tree dynamics - turnover, species comp
- Changes in stream ecology - altered flow patterns → impacts on aquatic & stream bank life
What were the findings of Ware et al. (2015) on the effects of fake roads (using speakers to mimic traffic) on wildlife?
- 31% of birds avoided the ‘road’.
- Birds that stayed near the road had lower body mass than control groups.
- Why? Likely due to a vigilance-foraging behavior tradeoff.
- Understory birds strongly avoid open areas (and therefore roads).
- Edge-loving gap and canopy species are less affected by roads.
How do roads cause barrier effects?
- Roads act as barriers to gene flow, leading to genetic differentiation among populations.
Smaller, partially isolated populations face greater extinction risks due to:
- Deterministic processes: Limited access to critical resources (food, shelter, space).
- Random demographic changes:
- Population size and structure fluctuations.
- Random environmental changes: Habitat disturbances or disasters.
List some methods to
to limit road mortality
- Barrier fencing
- Road signs (Do they actually work? Do people actually slow down?)
- Speed limits Esp in protected areas (What speed is appropriate?)
- How are they enforced?
- Windy roads (to slow traffic)
- Road closures
- Prohibit hunting (Difficult to enforce)
List some methods to enhance dispersal over roads
- Extend bridges over watercourses and riparian vegetation
- Allow natural canopy connections
- Canopy bridges
- Glider poles
- Overpasses
- Underpasses
Are road mitigation methods ecologically and cost effective?
- Often very ££, does it really protect pops?
- Problem: v few road mitigation actions are experimentally tested
- Built into initial plans (adequate EIA) vs after realise problem (inadequate/no EIA)
- Either way need rigorous scientific assessment
- E.g Optimal planning for mitigating the impacts of roads on wildlife Polak et al. 2014
What is the main proposal of Laurance et al. (2014) “A global strategy for road building”?
- Proposes a global zoning strategy to guide road construction.
- Balances environmental conservation with human development.
Identifies three types of zones:
- Avoidance zones: High environmental value where roads should not be built.
- Opportunity zones: Areas for road improvements to boost agriculture with minimal environmental harm.
- Conflict zones: Areas where road construction benefits agriculture but poses significant environmental risks.
Aims to minimize ecological damage while supporting sustainable development.
What is a bigger solution to road building
- Focus on preventing the most damaging roads from being built (e.g., in rainforests).
Recognize that not all roads are bad: - Bad roads: In ecologically sensitive areas like rainforests.
- Good roads: In agricultural lands to enhance development.
