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A global map highlights regions where road construction will have high environmental costs
India plans to construct over 0.8 million kilometres of roads by 2025 to connect every habitat in the country, as per the targets outlined in the government's Rural Road Development Vision. Worldwide, 25 million kilometres of roads are proposed to be constructed by 2050—a 60 per cent increase in road length from 2010—and nine-tenths of this new construction is expected in developing countries such as India. But construction of roads often harms biodiversity and destroys wild habitat. To weigh the potential benefits associated with road construction against their environmental impact, William Laurance, professor at James Cook University, Australia, and colleagues conducted a study and came up with a map that can help policymakers take informed decisions on where to construct roads.
The map highlights regions where road constructions will have high environmental costs. It is based on two factors: environmental values and road benefits. Environmental values are measured by integrating global data on three classes of parameters: biodiversity, key wilderness habitats and carbon storage and climate-regulation services of the local ecosystem. The researchers assigned a value between zero and one to each part of the globe. Regions with sensitive environments and, therefore, high environmental value scored close to one on a scale of zero to one. Similarly, road benefits were defined on the basis of potential increase in agricultural production resulting from better connectivity offered by roads.
The two sets of data were combined to generate a global map where every square kilometre (sq km) has been assigned a colour (see map). Green areas are those where road building would have relatively high environ-mental costs and only modest potential benefits for agriculture, while red-shaded areas have a high potential to increase agricultural production and low environmental values. Large parts of the Indian subcontinent fall under this category. Black and dark-shaded areas are “conflict zones” with high values on both the parameters, whereas white and light-shaded areas are of lower priority for both environment and agriculture.
In countries such as Indonesia and Madagascar, which have been assigned “exceptional environmental value”, the authors suggest adoption of alternative methods, such as ecotourism and harvesting the forest produce, to meet economic development goals. The authors note that roads are being constructed or are planned in regions that have high environmental values but only modest agricultural potential. These regions include the Amazon Basin, parts of the Asia-Pacific region and high latitude forests in the Northern Hemisphere. The map also shows that regions where road making is environmentally feasible exist in every continent. In total 12.3 per cent of the global land area has been mapped red. These include parts of central Eurasia, the Irano-Anatolian region, African Sahel and the Indian subcontinent. The study was published in Nature on August 27.
What ails India
What does the study mean for countries such as India which the map says has a huge scope for constructing roads with minimal environ-mental impact? According to Laurance, road construction even in such areas will have environmental impact (see `Unplanned roads can cause a lot of damage'). There are several examples to show this. Sanjay Gubbi of Mysore-based non-profit Nature Conservation Foundation says 23 leopards have died in road accidents in Karnataka in the past five years. He says environmental impact assessments done before laying new roads often ignore ecological issues resulting in loss of biodiversity and animal habitat. But this can be easily avoided.
Gubbi worked with the state government to realign a part of the Mysore-Mananthavadi road passing through the Nagarahole Tiger Reserve. “The realigned road helps 'defragment' wildlife habitat in addition to providing connectivity to 11 villages,” he says.
|`Unplanned roads can cause a lot of damage'
In the global road map you have generated, a large part of India is marked feasible for road making. Does this mean India need not worry much about environmental issues before laying roads?
No, it is not that simple. Areas in red are where road benefits would be greatest and where environmental values are less pronounced. But even in such areas, roads can and will have environmental impacts. For instance, it has been shown that tigers in India can move across large areas of settled and semi-settled land between tiger reserves-dispersing hundreds of kilometresin some cases. With increasing roads and agricultural intensification, the settled lands between reserves will become more hostile for wildlife such as tigers.
Also, of course, India has a number of exceptionally important environments where new roads can cause a lot of damage. Some examples would include the country's national parks, rainforests of the Western Ghats, parts of the Himalayas, and tropical and higher-elevation forests in Arunachal Pradesh.
However, in broad terms our study does indicate that there is much potential in India to improve agriculture. Road improvements, such as paving, can contribute to agricultural productivity by better linking farmers with markets and making fertiliser and agricultural technologies more accessible.
Lack of infrastructure has been a big issue in India. What key issues should be kept in mind while planning new roads?
Our key points are that roads that penetrate into wilderness areas or parks can cause a great deal of environmental damage, and so one has to be very careful about planning new roads.
Our study tries, on a broad global scale, to underscore the kinds of situations where roads can be most harmful and where they can be most beneficial. Actual road planning will also need to incorporate local-scale information, because the global datasets we had access to are often too coarse for actual road-planning.
How should areas that appear ecologically sensitive on your map but already have roads laid out be dealt with?
Many environmentally important areas around the world already have roads. A key priority is to limit further road proliferation in these areas, and even to close some existing roads if it appears that they are causing a lot of environmental damage and generating only limited benefits.
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