Urban Expansion Impedes Biodiversity Conservation

Often urban expansion occurs concomitantly with economic growth in developing countries, not to mention land use change including the conversion of forest to agricultural land. A new study in Landscape and Urban Planning suggests that expansion of Panama City and Colon, both of which are surrounded by richly biodiverse rainforests, could result in future biodiversity loss.

Increased urbanisation is anticipated in these cities after a planned expansion of the shipping canal, and it is likely that this will result in increased forest loss. This could be exacerbated by the rural population, 61 per cent of whom live below the poverty threshold, and presently have no alternative but to remove standing forest for agriculture and income purposes.

The researchers looked at potential socio-economic and biophysical correlates of biodiversity loss including population density and growth, road density and poverty levels, rainfall, forest age and land use. They found that population wealth was linked to conversion of land to urban areas, i.e. the more wealth the more conversion. The researchers also found that agriculture was expanding into mature forests.

The rainforests offer a wealth of ecosystem services including the provision of clean water, flood and landslide prevention through water capture not to mention the carbon storage and climate regulating influences. However if an ecosystem services approach is not applied to the forests appropriately, it is likely that, as affluence increases in the urban areas, the true value of the forests will be taken for granted. This could result in increased forest clearance for what is perceived as more valuable urban development projects.

The authors suggest that ecotourism and agroforestry could provide alternative less destructive economic opportunities. If alternatives are positively explored it could assist the rural population move above the poverty threshold without destroying the valuable forests which they, and we all depend upon.

Source: Rompré G, Robinson WD and Desrochers A (2008). Causes of habitat loss in a Neotropical landscape: The Panama Canal corridor. Landscape and Urban Planning. 87: 129-139.

Soil Biodiversity Integral to Carbon Cycling

The respiration of soil is a key function in the carbon cycle, moving carbon from the ground to the atmosphere.

Peatland across Northern Europe occupies somewhere in the region of 3.5 million km2 and holds one third of the world's soil carbon. These areas are under pressure from increased agricultural activity, which accelerates the net loss of carbon dioxide. Theory and practice suggests that afforestation will result in net carbon uptake and reduce carbon loss to the atmosphere from soil respiration. Although soils are thought to act as a sink for carbon, land-use change such as agriculture alters the way that carbon dioxide is emitted.

Currently tree plantations are believed to be a worthwhile mitigation technique against climate change. However, in a research paper published in Soil Biology and Biochemistry, researchers found that previous agriculture on afforested land led to higher soil respiration than undisturbed areas, up to decades after afforestation.

At present, European legislation is placing an emphasis on the role of afforestation in combating climate change. This research suggests that further work is required into the effects of climate change on soil biodiversity and the subsequent effect on the carbon cycle.

BES members and readers of the blog are invited to discuss this article.