Landscapes Forest and Global Change - ESA - Escola Superior ...

S.R. Freitas et al. 2010. The effect of highways on native vegetation and reserve distribution in the State of São Paulo
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by them. Between the ecoregions (Olson et al. 2001), Serra do Mar coastal forests were the most
affected by roads (51%). However, in relation to its cover, mangroves have more of its cover
affected by roads (16%). About 55% of nature nature reserves were affected by roads. Five of
them showed more than 30% of their territory affected by roads.
There is more native vegetation cover as road distance increases (Figura 1). This relationship
was nearly logistic for expressways (Figure 1).
4. Discussion
The State of São Paulo has a lower road density (0.15 km/km 2 ) than that considered as
maximum for sustain populations of big predators (0.60 km/km 2 ; Forman and Alexander 1998).
However, those roads affect the distribution of native vegetation and threat the efficiency of
nature reserves. Near roads could cause a significant increase of mortality rates for many
wildlife populations, even overcoming hunting (Forman and Alexander 1998).
Almost 10% of State of São Paulo is ecologically affected by roads. Forman (2000) found a
double proportion (about 20%) to United States of America. However, the State of São Paulo
has a very lower road density than USA (0.41 km/km 2 ; Forman 2000), indicating that more
native vegetation is under threat of roads in our study area. Even many states of USA have
higher road densities than State of São Paulo (0.15 km/km 2 ): Misouri (1.89 km/km 2 ), Arkansas
(1.23km/km 2 ) and Oklahoma (1.18 km/km 2 ; La Rue and Nielsen 2008).
Laurance et al. (2009) state that non-paved roads represent a lower impact on vegetation and
wildlife in tropical forests than paved roads because they usually are inaccessible during raining
season (summer). However, our study showed that non-paved and paved roads affect more than
highways and expressways because they are more abundant and spread all over the territory,
showing higher densities (0.06 km/km 2 and 0.07 km/km 2 respectivelly) than highways (0.01
km/km 2 ) and expressways (0.01 km/km 2 ).
As expected, the dominant vegetation type - Serra do Mar Coastal Forests - was the most
affected by roads. Serra do Mar Coastal Forests is distributed along coastline as well as many of
road network in Brazil, representing one of the most important connection axis for national
transportation (north-south). However, in proportion mangroves are highly affected by roads for
the same reason.
Half of natural reserves is affected by roads. Five of them have more than 30% and three of
them have more than 60% of their territory affected by roads, which represents a threat for their
biodiversity. Roads facilitate hunter access and increase the probability of collision by vehicles
(Laurance et al. 2009). Nature reserves near roads are probably under more conflicts with
human population and more vulnerable to environmental degradation.
There is more native vegetation as far as the road is. Roads act as atractor to land use and
deforestation (Nagendra et al. 2003; Freitas et al. 2010). For instance, in the Amazon Forest,
about 95% of deforestation occurred at most 50 km far from roads (Laurance et al. 2009).
Expressways are not too densely distributed as other road types, however they show a nearly
logistic relationship to native vegetation cover indicating a strong negative effect to the nearby
native vegetation. Thus, road distance could be used as indicator to predict the distribution of
native vegetation in the future. We suggest that in order to improve conservation and restoration
strategies, the effect of highways should be carefully considered, prioritizing remote areas.
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.