Sea level rise, desertification and biodiversity

In the previous articles, I wanted to know more about the costs and assessment of sea level rise and desertification. I deplored that biodiversity was not taken into the account of the costs of the process. Though, we know the free service to the societies of the biodiversity. We know that a loss of biodiversity would have some effects on the economy. Menon et al. (2010) tried to assessed globally the biodiversity drop induced by a sea level rise of one meter to six meters by 2100. One meter, because it is close to the highest predictions of the IPCC, and six meter because these prediction did not take into account the acceleration of the thaw of the greenland ices heets (Menon et al, 2010). They found that the biodiversity would be proportionally affected to the importance of the SLR and its speed. Also, a six meters rise of the sea would have some catastrophic effects for biodiversity, especially on the ecosystems as the mangroves which are considered as very rich. From displacement inland of the ecosystems to their fragmentation and the extinction of endemic species, there is a gradation of the impacts (Menon et al, 2010). 

The paletuviers, the vegetal species of the mangroves.

Desertification has also some effets on biodiversity. As I wrote it in some precent article, to Bestelmeyer, 2005), the shift from grassland to shrubland which is considered as desertification, changes the ecosystem but the shrublands have a richer ecosystem (Bestelmeyer, 2005). However the next steps of desertification, from Shrublands to steps and from steps to reg and erg, we cannot state that the biodiversity is not negatively affected. Of course, it depends of it intensity. 

From the shrubland to the reg, a loss of biodiversity

Thus, these two processes have some impact on the biodiversity proportionally to their importance. The ecosystems are displaced, fragmented or diminished by the extinction of some species. Moreover, by moving inland, the displaced ecosystems  put some pressure on some other ecosystems maybe already pressured directly by the human activities...

Bibliography: 

Bestelmeyer, B.T. 2005. Does desertification diminish biodiversity? Enhancement of ant diversity by shrub invasion in south-western USA. Diversity and Distribution. No. 11. p45-55

Menon et al. 2010. Preliminary global assessment of terrestrial biodiversity consequences of sea-level rise mediated by climate change. Biodiversity conservation. Vol.19. p1599-1609.

The cost of sea level rise in western countries

Many articles claim to assess the cost of the sea level rise. However, the approaches are not always comparable. For example, the cost of the SLR in the developing countries having no sea-walls cannot be compared with the one of developed countries already having many protections. Also, for the developed countries, the assessment studies do not always have the same objectives. Some try to assess the macro-economic cost and thereby the results are clearly dedicated to the governments (Bosello et al. 2012), some are more dedicated to the insurance company (Michael, 2007) by providing an assessment at a bigger scale, some are dedicated to the cities etc. The abundance of scientific articles assessing the cost of the sea level rise attests of the complexity of the task resulting of the uncertainty of the forecast. 

Bosello et al. (2012) assessed the economic impacts of the SLR in Europe. They reckon the cost of adaptation and the cost of the direct damages and economic loss without adaptation in order the know more about the best solution. In their conclusion, they attest that some countries would save more money by not adapting themselves. However, their analysis is only economic and do no consider the danger for some human life and their analysis does not consider the indirect economic cost, for example, the impact on tourism. To give you a rough size,from the highest SLR scenario of the IPCC, they assess the adaptation costs at 803 million euros per year by 2020 and 2,3 billion euros by 2080 in Europe, an we know that the observed SLR have followed the highest prevision of the IPCC.  

Zhang et al. (2011) focused on a much smaller area and took less risks on the estimation as they assessed the adaptation cost per properties in the Florida Keys from 2000 to 2100. In these low islands, a rise of 0.6 meter by 2100 would inundate 70% of the area and 12% of the real properties which are estimated to 39 billion dollars. 

At the same scale, Michael (2007) assessed the damage due to the higher episodic flooding occasioned by the SLR without speculating on their frequency in three areas of the Maryland. For an three feets (about 90cm) scenario of SLR, the growth of the flood damage goes from more than a million dollars to 18 million dollars per flooding depending of the elevation of the area and on the intensity of the event. 

All these results cannot be compared but permit to realize the huge cost of the SLR. They also attest of the diversity of the impacts of the SLR. However, the assessment cannot be reduced to an economic cost as the SLR associated with extreme events could have some impacts on human lifes and biodiversity, even more in the developing countries.

Bibliography: 

Bosello, F. et al. 2012. Economic impacts of climate change in Europe:

sea-level rise. Climatic change. No. 112. p63-81

Michael, J.A. 2007. Episodic flooding and the cost of sea level rise. Ecological economics. No. 63. p149-159.

Zhang, K. et al. 2011. Assessment of sea level rise impacts on human

population and real property in the Florida Keys. Climatic Change. No. 107. p129-146

Assessing desertification, a complex task

Desertification has been defined as "the degradation of lands in arid, semi-arid and dry sub-humid areas resulting from various factors including climatic variations and human activities". The definition of the United Nation Convention to Combat Desertification (UNCCD) suffers from its lack of precision (Barbero-Sierra, Margues & Ruis-Perrez, 2013).

Is what we call desertification comparable to the quick shift of the Sahara from green to desert 6000 years ago, at the mid-Holocene? This change resulted from the change of the earth orbit which moved southward the ITCZ and the monsoon (Blom et al. 2004).  It is important to grade the desertification. Nevertheless, if the SLR can be assessed easily by comparing the absolute SLR and the subsidence of the continent, the definition of the desertification does not implies a clear assessment.

When the soils loose their fertility

What is the degradation of lands? Bestelmeyer (2005) considers the shift from grasslands to shrublands as a desertification.  However the author does not link it to a drop of the diversity. However he underlines the effects on the agricultural production. Indeed, the livestock needs grasslands. Is it the degradation of lands  a drop of the agro-pastoral capacities of the soils? In India after the green revolution, the growth of irrigated lands which lead to a salinization of the soils and a loss of their fertility, many authors have pointed the risks of desertification. 

Which human activities lead to desertification? Of course, the intensive agriculture which does not consider the needs of the soils affects their fertility. As long as the agriculture, pick out of the ground more than it can sustain, the fertility of the soils will decrease. Barbero-Sierra, Margues & Ruis-Perrez (2013) also consider the sprawl urbanization as a cause of desertification by sealing the grounds and by converting the agricultural fields in low density urban areas.

The danger of intensive agriculture in Spain

The climate change causes of the desertification are easier to understand. An arridification, a drop of the precipitation etc.
Veron et al. (2006) assessed the desertification thanks to many indicators relative to the plant cover, the erosion, the salinization. However Barbero-Sierra, Margues & Ruis-Perrez (2013) state that the reversibility of the desertification has to be assessed to understand the threats on the population and on the biodiversity and to get a better idea of the necessary actions to reverse the process. The intensity of the factors shows immediately the reversibility of the process. Some actions could be taken on some target areas where the results could be more successful.

Barbero-Sierra, C. Margues, M.J. & Ruis-Perrez, M. 2013.The case of urban sprawl in Spain as an active and irreversible driving force for desertification. Journal of Arid environments. Vol. 90. p95-102. http://www.sciencedirect.com/science/article/pii/S0140196312002820

Bestelmeyer, B.T. 2005. Does desertification diminish biodiversity? Enhancement of ant diversity by shrub invasion in southwestern USA. Diversity and Distribution. No.11. p45-55

Blom et al. 2004. The Green Sahara: Climate Change, Hydrologic History and Human Occupation.
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4977129

Veron, S.R. Paruelo, J.M., Oesterheld, M. 2006. Assessing desertification. Journal of Arid environments. No. 66. p 751-763

Ancient impacts of Sea Level Rise on societies

The sea level has always been changing. While we are facing the sea level rise and wondering how much it will cost us, it seems interesting to know which impacts it had on human activities in the past. I found some articles which bring some very interesting and surprising arguments. 

I learnt that sea level rise played an important role in the important period of migration. Indeed, Turney and Brown (2007) reports that the abrupt sea level rise of 1.4 meter around 8350 BP 8230 BP and  explains the salt intrusions in the black sea and thereby the migrations of the Neolithic people to Europe, spreading the neolithic across Europe. 

Moreover, the colonization of the small pacific island by humans had often seemed mysterious. Why have people migrated from island to island sometimes separated from very long distances? Nunn (2007) States that the sea level changes had some very important impacts on these societies. Sea level rise was threatening the crops by erosion whereas sea level fall was dragging the water table down and undermining the yields. Thus the periods of rapid sea level changes have been followed by perilous migrations in the Pacific Islands. 

At the time of globalization, innovations do not need massive migrations to be spread. At the opposite, innovations are spread to not let the massive migrations happen: the advanced countries sell and export their resilience to sea level rise ( Chu, 2013). 

Bibliography: 

Chu, J. 2013. How the Netherlands became the biggest exporter of resilience. Co.exist. http://www.fastcoexist.com/3020918/how-the-netherlands-became-the-biggest-exporter-of-resilience?partner=newsletter

Turney, C.S.M. & Brown, H. 2007. Catastrophic early Holocene sea level rise, human migration ad the neolithic transition in Europe. Quaternary Science Review. No. 26. p2036-2041

Nunn, P.D. 2007. Holocene sea-level change and human response in Pacific Islands. Earth and environmental science transaction of the royal society of Edinburgh. No. 98. p117-125.