Roads

Question 1

The impacts of roads on biodiversity

Answer 1

Drivers of rainforest loss

Proportion of drivers may change across the globe but all activities are facilitated by roads

• subsistence agriculture
• logging
• intensive agriculture
• ranching/pasture

Question 2

Roads facilitate economic and social development

Answer 2

Market access for timber & agricultural products
Access to remote areas
Lower costs of land clearing
Cheap labour

Question 3

Ecological effects of roads

Answer 3

Habitat loss
Road mortality
Edge effects
Barrier effects and fragmentation

Question 4

1. Habitat loss

Answer 4

Habitat loss is the initial and most obvious impact of roads/powerlines

Road/powerline networks may alter or destroy scarce natural habitats

Facilitate further clearings

Question 5

In brazisial amazonia

Road network doubled: 87,000 to 161,500 km

Answer 5

> 95% Amazonian deforestation within 50 km of a road (Laurance et al. 2009 TREE)

Question 6

Adeney et al.

Reserves protect against deforestation fires in the amazon

Answer 6

12 fires 10km from road vs. 3 fires 10km from road

1 fire 50km from road vs. no fire 50km from road

Question 7

2. Road mortality

Answer 7

Significant population sink (sources/sinks & cassowaries)
Features of susceptible wildlife: slow-moving, arboreal, terrestrial or flying, nocturnal or crepuscular

Question 8

Road mortality

Answer 8

Species attracted to roads/roadsides such as amphibians, reptiles, herbivores & frugivores, carrion feeders & predators
Species with nearby habitat – wetlands, grassy verges, fruit
Species with large-area requirements

Question 9

Road mortality

Answer 9

Road features that increase mortality rates: width, traffic speed & volume, roadside vegetation & adjacent habitat
Significant population sinks can occur for rare and endangered species

Question 10

Brown and Brown, 2013

An estimated 80 million birds are killed by colliding with vehicles on U. S. roads each year [1], and millions more die annually in Europe [2] and elsewhere. Losses to vehicles are a serious problem for which various changes in roadway design and maintenance have been proposed [3]. Yet, given the magnitude of the mortality reported for some species [4], we might expect natural selection to favor individuals that either learn to avoid cars or that have other traits making them less likely to collide with vehicles.

Answer 10

If so, the frequency of road kill should decline over time. No information is available for any species on whether the extent of road-associated mortality has changed [2]. During a 30-year study on social behavior and coloniality of cliff swallows (Petrochelidon pyrrhonota) in southwestern Nebraska, we found that the frequency of road-killed swallows declined sharply over the 30 years following the birds’ occupancy of roadside nesting sites and that birds killed on roads had longer wings than the population at large.

Question 11

Road mortality impacts on different taxa

Answer 11

Amphibians suffer greater losses

Increased road width causes declines in mortality

Question 12

Road-related mortality –

Answer 12

bush meat hunting

Question 13

3. Edge effects

Answer 13

Cut and fill
construction
Impeded water flows

Question 14

Edge effects - pollution

Answer 14

Chemical emissions may lead to pollution of air, soil and water adjacent to roads
Energy emissions in the form of noise, headlights, vibrations & movements may disturb sensitive wildlife

Question 15

Edge effects – habitat decay

Answer 15

Changing microclimatic conditions –humidity, light, temperature; wind speed & turbulence
Increased tree damage and death
Increased tree dynamics - turnover, species composition

Changes in stream ecology - altered flow patterns  impacts on aquatic & stream bank life

Question 16

Edge effects - wildlife

Answer 16

Ware et al., 2015 Phantom road experiments reveals traffic noise is an invisible source of habitat degradation 31% of birds avoided the ‘road’
Birds that stayed had lower overall body condition (mass/length)
Laboratory experiments suggest vigilance-foraging behaviour tradeoff as a mechanism

Question 17

Do all species suffer from roads?

Laurance et al. 2004 Conserv Biol

Answer 17

Edge avoidance by understory birds

Vs. edge loving by gap & canopy spp

Question 18

4. Barrier effects of linear clearings

Answer 18

Divide up habitats & wildlife populations?
Roads can be barriers to gene flow
 genetic differentiation among populations?
Smaller partially isolated populations at greater risk of extinction due to deterministic processes
limiting a critical resource (food, shelter or space)
Random demographic changes
Random environmental changes

Question 19

Barrier effects

Answer 19

Features that influence the permeability of linear clearings
Clearing characteristics - width, traffic volume & speed, adjacent vegetation, road cuttings
Species characteristics – behaviour, mobility, habitat specificity (generalist vs specialist)

Question 20

Bird movement responses to roads?

Answer 20

Passive obs:

• birds cross
• birds do not cross

Experimental translocations:

• Birds can cross when forced (local mvmts disrupted)
• Birds do not cross (dispersal disrupted)

Question 21

Observation: Road avoidance

Implications
Dispersal is a principle factor determining wildlife survival
Populations could become isolated by roads

Answer 21

Experimental translocations
Highway clearing
50 – 75 m wide

MSF
Rapid return
3-19 hrs
Understory
24-48 hrs
Terrestrial
No return
24-48 hrs

Question 22

Mitigation methods

Answer 22

AIM: To increase permeability of roads

1) Decrease road widths, allow regrowth and canopy connections (but more road kill)
2) Extend bridges over watercourses to include terrestrial vegetation
3) Reduce road speeds (windy roads better) in protected areas
4) Prohibit hunting (but can it be enforced?)

Question 23

Mitigation methods-road signs

Answer 23

Do they work?

Do people actually slow down?

Question 24

Mitigation methods-road closures

Answer 24

Only on small roads

Economic incentive to protect species?

Question 25

Mitigation methods-canopy bridges

Mitigation methods -overpasses

Answer 25

Mitigation methods-glider poles

Mitigation methods -underpasses

Question 26

Mitigation – retrospective?

Answer 26

Mitigation is retrospective
Often very expensive, does it really work?
Need a bigger solution to prevent most damaging roads from being built…

Question 27

A global map for road building

Laurance and Balmford

Answer 27

Bad roads, good roads?
25 million km new road by 2050
= 60% increase in total length from 2010
90% construction in developing nations

Question 28

A global strategy for road building

Answer 28

Environmental-values layer
Terrestrial biodiversity
Key habitats and wilderness
Environmental services

Road-benefits layer
Suitable for agricultural intensification
New roads or improved roads will promote increased production

A global roadmap
Environmental-values X road-benefits layers
Priority road-free and agricultural areas
Dark shades - conflict areas
Light shades - low-priority areas

Question 29

Current events: Serengeti highway threatens world’s greatest migration

Answer 29

• Funding offered for detour to communities ~ 2011 German govt. offered $23.5 million & World Bank
• Jan 2012 MOU Tanzania & China to construct railway
• July 2012 – Tanzanian govt claim only a gravel road will be maintain through the park
• Jan2013 – court case challenging Tanzania’s decision to build a highway
• July 2014 – East African court of Justice rules against paved highway

Question 30

Policy recommendations

Answer 30

Roads are major drivers of forest & biodiversity loss
EIA of roads –Reduce road widths to maintain connectivity
Mitigation strategies (but limited evidence for value)
Maintain large roadless areas of intact habitat – a conservation priority
Direct roads to areas with yield gaps (& low biodiv)
Carbon-trading (REDD+) could direct payments to countries in conflict zones?