“How Much Land Does a Man Need?”
Count Lyev Nikolayevich Tolstoy (1828–1910) It is a factious reality that all the creatures upon this globe have to live together in harmony. In Genesis 7:15-17 (Old Testament) the description of man and animal contact is very much emphasized : “They had with them every wild animal according to its kind, all livestock according to their kinds, every creature that moves along the ground according to its kind and every bird according to its kind, everything with wings.15 Pairs of all creatures that have the breath of life in them came to Noah and entered the ark.16 The animals going in were male and female of every living thing, as God had commanded Noah. Then the LORD shut him in.” We doubt if the zoonotic concept was clear at that time, but the story describes the close relationship between humans and other“God created”creatures.
The only problem, to evolve into a serious one, was the humans themselves.
Since the start of the 20th century, human population has more than tripled its size from∼1.8 to∼6.9 billion (Figure 1.1.1) (Steck, 2010). According to United Nations database, there are several scenarios on of the human population prospect, some based on status-quo: women’s productivity does not change [birth rate remains 2.82 children/woman (constant progression, red line)] and therefore the population will continue to expand to∼13 billion in 2050; the more optimistic ones are based on the hypothesis that the birth rate will drop from 2.82 to 2.15 children/woman, including a life expectancy increase from 65 to 76 years [blue lines: high and low estimation dotted lines and medium continuous line] to range from 8 to 11 billion (9 billion medium) in 2050 (Figure 1.1.2). There are many reasons for this huge increment, but perhaps the most egregious one is the advanced medical treatment (scientific revolution) that followed the industrial revolution. Wars, famine, natural catastrophes, economic scrambles, etc. did not affect the global population’s exponential growth as medicine did. If we want to understand this phenomenon, perhaps the most perceptive step is to glance at the records of the deceased registered throughout the centuries by the Catholic Church in Europe of the Middle Ages. An average human life of 40 years was the upper limit while people reaching the advanced ages of 50 and 60 were considered to be the village elders! These days, a retired person in his late 60’s is still considered “young”. In nature, the animal population is largely controlled by food availability, territory and epizootics which are in harmonious balance with environmental factors. Interestingly, we (the humans) are competent to
control these populations for our own benefit, for instance animals’ domestication in large numbers.
However, who controls our own population? There are two main factors that might control it: our progressive awareness and environmental capacity. Of the awareness part, in spite of cultural “bottle necks” (illiteracy, diverse cultural and religious norms), there is a general endorsement that our population cannot grow continuously at the same rate and has to slow down or enter a “zero”growth kinetic. Of the environmental capacity part there is“no need”for direct awareness, as it blows itself up in our face. Increasing industrial capacity to its limits created a new problem of intense pollution that in turn affected the population’s well-being and its environment. It is not within our scope to analyze different models as we are neither demographers nor population scientists, but the common sense of microbial growth can be in large applied to the human population based solely on reproduction, though the time scale is different. Immigration or migration cannot be considered as they do not change the population size but only its composition. In terms of socio-economic composition, it can be in general stated that the
“North”is rich and“South”is poor. Indeed, large areas of the South include more developing countries than the “North” that harbors more developed countries. There is no need to say that migration/ immigration from the“South”to the“North”is a continuous process, with some positive aspects related to population growth (e.g., education merged with socio-economic progress tend to impact birth rate).
Another interesting trend in human population is the continuous relocation from rural to urban areas in developing countries (Figure 1.1.3). The trend is linked to economic aspects such as rapid industrial development in urban areas and decline in agricultural activities that are less profitable and demand long and tiresome labor. According to 2005 FAOSTAT (Food and Agricultural Organization statistical databases), at that time the world population of 6.4 billion was divided in 49% urban and 51% rural populations. As a result, the socio-economic division of urban population between high and low/middle Figure 1.1.1. Historical world population growth from 1750 to 2050. (Source: United Nations Population Division)
Environmental Aspects of Zoonotic Diseases 4
Figure 1.1.2. World population evolution. (2009). InUNEP/GRID-Arendal Maps and Graphics Library.
Retrieved 10:36, April 20, 2011 from http://maps.grida.no/go/graphic/world-population-evolution, credit toPhilippe Rekacewicz (Le Monde diplomatique)
1960 1970 1980 1990 2000 2010 2020 2030 0
1 2 3 4
Urban and rural population in less developed regions (billions)
Rural
Projections Estimates
Urban
Figure 1.1.3. Trends in urban and rural populations, less developed regions, 1960-2030 (estimates and projections) . (2009). InUNEP/GRID-Arendal Maps and Graphics Library. Retrieved 21:34, May 4, 2011 from http://maps.grida.no/go/graphic/ trends-in-urban-and-rural-populations-less-developed-regions-1960-2030-estimates-and-projections. credit toHugo Ahlenius, Nordpil
Human population and socio-economic distribution 5
1
1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050
Asia
Sources: Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, World Population Prospects: The 2004 Revision; Global Footprint Network, 2005.
Figure 1.1.4. World Population. (2006). InUNEP/GRID-Arendal Maps and Graphics Library. Retrieved 21:28, May 4, 2011 from http://maps.grida.no/go/graphic/world_population, credit toEmmanuelle Bournay (Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, World Population Prospects: The 2004 Revision; Global Footprint Network, 2005)
Selected terrestrial biodiversity hotspots Selected major wilderness areas Prevalence of stunting among children
under five, in areas of >2 inhabitants/sq km
0 95%
No data Low population density
Sources: FAO 2004, Landscan 2002, Conservation International 2004
/
Environmental Aspects of Zoonotic Diseases 6
In relation to environmental sustainability (i.e., how many people can be supported at a certain consumption level) it seems that the growing world population will reach a point (by 2050) that ∼2 billion people will be expected to be sustained at a high income consumption level, while∼4 billion at middle income consumption level and ∼3 billion at a low income consumption level, of a total of ∼9 billion people (Figure 1.1.4). The predicted 2050 low income population (∼3 billion people), in other words very poor populations, will reside largely in the geographic areas with high biodiversity (Figure 1.1.5). Consequently, without much choice, this population will unsustainably extract resources threatening biodiversity and their own health. Health problems expressed as stunted growth in children are also very apparent in these areas where poverty and high population density coincide. Poverty (or low income) is also an indicator of economic development however, low incomes can be also found in highly developed countries (e.g., USA, Russia, etc.) although masked by overall calculations for the entire population. The high income countries consume and also produce more waste but due to advanced technology and lower population density they will be able to sustain themselves. In contrast, the new members of the“middle income countries club”such as China and Indonesia will have deal with intense economic growth versus resources depletion and energy use that may become a“bottle-neck”as a result of their highly dense population! (Figure 1.1.6).
Figure 1.1.6. Population by income level. (2006). InUNEP/GRID-Arendal Maps and Graphics Library.
Retrieved 21:38, May 4, 2011 from http://maps.grida.no/go/graphic/population-by-income-level, credit to Emmanuelle Bournay [World Bank, 2006 (figures for 2005)]
Human population and socio-economic distribution 7
In summary, one of the major global holdups is population growth beyond the sustainability of our planet, coupled with other phenomena also related to population density: climate change, waste production and pollution, biodiversity decline, etc. (Dasgupta, 1995).
We wonder if even one individual among the global big poor population would understand the following equation (representing Gini coefficient-inequality measure) (Milanovic, 2002):
Without much knowledge of economics and mathematics, this poor population certainly understands the everyday burden of food and water supply, health care and lack of reliable education and living conditions.
All these parameters are directly linked to the spread of infectious diseases as shown in Figure 1.1.7.
Diseases caused by various pathogenic organisms (universally called infectious diseases) described along this book, are significantly correlated to socio-economic level of large populations. Figure 1.1.7 shows a
0 100 km
Figure 1.1.7. Socioeconomic status and cholera spread in South-Africa (Kwazulu-Natal January 2001) (2002). InUNEP/GRID-Arendal Maps and Graphics Library. Retrieved 12:37, January 20, 2011 from http://maps.grida.no/go/graphic/poverty-and-cholera-in-kwazulu-natal-january-2001, credit to Philippe Rekacewicz, UNEP/GRID-Arendal (Statistics South Africa (www.statssa.gov.za), World Bank and South African Department of Health. Adapted by UNEP/GRID-Arendal)
Environmental Aspects of Zoonotic Diseases 8
> 100
20 50 75
< 9 No data Infant mortality as poverty indicator
Infant deaths per 10 000 live births, adjusted to the year 2000
Source: CIESIN 2005
Figure 1.1.8. World poverty distribution. (2008). InUNEP/GRID-Arendal Maps and Graphics Library.
Retrieved 16:48, May 7, 2011 from http://maps.grida.no/go/graphic/world-poverty-distribution, credit to Hugo Ahlenius, UNEP/GRID-Arendal (Center for International Earth Science Information Network (CIESIN), Columbia University. 2005. Global subnational infant mortality rates. Available at: http://www.ciesin.columbia.
edu/povmap/ds_global.html (Accessed April 28, 2008)
High total economic loss risk top 3 deciles at risk from:
Drought only Geophysical only Hydro only Drought and hydro Geophysical and hydro Drought and Geophysical Drought, Hydro and Geophysical
Figure 1.1.9. Natural hazard hotspots, by risk type. (2007). InUNEP/GRID-Arendal Maps and Graphics Library. Retrieved 16:53, May 7, 2011 from http://maps.grida.no/go/graphic/ natural-hazard-hotspots-by-risk-type, credit to Hugo Ahlenius, UNEP/GRID-Arendal (Center for Hazards & Risk Research. 2005. Natural Disaster Hotspots - A Global Risk Analysis: Global Multihazard Frequency and Distribution. http://www.ldeo.
columbia.edu/chrr/research/hotspots/coredata.html (Accessed June 1, 2007)
Human population and socio-economic distribution 9
75% of all poor people still live in rural areas, where they are heavily dependent on natural resources such as, soil, water, forests and fisheries (Figure 1.1.8). Figure 1.1.8 also represents poverty expressed by the infant death rate, an obvious measure of deprived health care and malnutrition in these areas. Many developing countries own these natural resources and therefore are still able to support a potential minimal wealth for poor people and their communities. However, as many of these natural resources are renewable they need to be properly managed in order to support these population in the long term.
Poverty alleviation can occur through improved natural resource management but also by birth control in order to reduce the stress of the human population on natural resources for a sustainable development.
Another interesting point related to poverty is the link to global hot spot disasters (droughts, floods, earthquakes, etc.) (Figure 1.1.9). With climate change, the frequencies of certain natural hazards are expected to increase. Figure 1.1.9 represents a graphical overview of an analysis of hazard exposures and historical vulnerability some natural hazards, together with population distribution and economy.
Obviously, poor populations will suffer the most from these hazards and their ability to overcome such disasters is close to nil.
Diseases caused by various pathogenic organisms (universally called infectious diseases) described in this book are significantly correlated to socio-economic level of large populations.
1.1.1 REFERENCES
Dasgupta, P.S. (1995) Population, poverty, and the local environment.Sci. Am.272, 26–31.
Milanovic, B. (2002) True world income distribution. 1988 and 1993: First calculation based on household surveys alone.Econ J (London)112, 51–92.
Steck, T.L. (Lead Author); United.nations (Content Source); Peter Bartelmus Dr., Arun Sharma (Topic Editor)“Human population explosion”. In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth July 26, 2010; Last revised Date December 14, 2010; Retrieved May 5, 2011,http://www.eoearth.
org/article/Human_population_explosion?topic=54245..
Environmental Aspects of Zoonotic Diseases 10
Chapter 1.2 Climate
“Climate is what we expect, weather is what we get.”
Mark Twain (1835–1910) It is not within the scope of this brief chapter to solve the debate whether climate changes are a consequence of human activity or just a natural succinct phenomenon that occurs periodically for millions of years (see ice age). The balance between entering energy (sun radiation) and leaving energy (energy reflected by earth), where the atmosphere plays a crucial role as a thermal isolator, are the main components that impact earth’s climate (Figure 1.2.1). Our contribution to greenhouse gases is continuous through industrial development, increasing ground and air-traffic and incineration.
Natural climate forcings (forcing is a destabilizing factor of the above system) are mainly natural (e.g., the sun’s brightness, small variations in Eart’s orbit and axis rotations and volcanic eruptions) but also manmade (e.g., aerosol production, CO2and greenhouse gases emission and deforestation) (Kirilenko and Sedjo, 2007) (Figure 1.2.2). Nevertheless, over a century global warming is an undisputed scientific fact, expressing itself in rapid mountain glacier retreat and a corresponding sea level rise (Bergeret al., 2010) (Figure 1.2.3).
Warming has its impact on major ecological and biological systems including a large variety of parasites, their vectors and the final hosts. Varouet al.(2007), reviewing the tick-borne viral disease Crimean-Congo hemorrhagic fever (CCHF), reported that climate changes may affect CCHF epidemiology through influencing survival and reproduction of Hyalomma ticks and their hosts. For example, mild winters preceded outbreaks of this virus in Turkey and Kosovo, while interruption of agricultural activities by the reintroduction of cattle and sheep, a decrease in hare hunting and conversion of floodplains into agricultural land have been associated with CCHF outbreaks in Russia, Bulgaria, former Yugoslavia and Turkey. A different view on another tick-borne disease (tick-borne encephalitis-TBE virus) has been published by Randolph (2010). The author suggested that climate change alone could not explain the increase pattern and upsurge of the TBE virus due to its uniformity (e.g., in Baltic countries) and other factors seem to be more relevant to the phenomenon. Among these factors, Randolph (2010) suggested:
“1) agricultural reforms resulting in changed land cover and land use, and an increased reliance on subsistence farming; 2) reduction in the use of pesticides, and also in the emission of atmospheric
pollution as industries collapsed and 3) increased unemployment and poverty, but also wealth and leisure time in other sectors of the population, as market forces took hold”.
In Portugal, Leishmaniases, a zoonosis endemic in the Mediterranean basin, has shown a significant increase in cases number and a shift from pediatric to adult cases (mainly immunocompromised, HIV/AIDS). The authors suggested that climate amelioration may increase Leishmaniasis’ arthropod vector, the phlebotomine sand flies, densities and activity favoring higher incidences (Campino and Maia, 2010). In Belgium, Nephropathia epidemica (NE), an emerging rodent-borne viral disease had shown a sharp increase in incidences for more than a decade (Clement et al., 2009). The authors suggested that bank voles might be responsible for this hantavirus through their known cyclic population peaks impacted by climate warming. In a recent study from Germany, an outbreak of Leptospirosis was recorded among strawberry harvesters (Desai et al., 2009). Leptospirosis is primarily known to be present in tropical countries with connection to agricultural exposures, and much less in temperate countries (such as Germany). The authors suspected that direct contact of humans (with hand lesions) Figure 1.2.1 Radiation balance between sun and earth. (Adapted from NASA site http://earthobservatory.
nasa.gov/Features/EnergyBalance/page1.php)
Environmental Aspects of Zoonotic Diseases 12
Figure 1.2.2. Climate change global processes and effects. (2009). InUNEP/GRID-Arendal Maps and Graphics Library. Retrieved 23:10, April 26, 2011 from http://maps.grida.no/go/graphic/ climate-change-global-processes-and-effects1, credit to UNEP/GRID-Arendal
1.6 - 2.1 1.2 - 1.6 0.8 - 1.2 0.4 - 0.8 0.2 - 0.4 -0.2 - 0.2 -0.4 - -0.2 -0.8 - -0.4 Insufficient data Temperature anomalies
2001-2005 Mean surface temperature anomaly relative to 1951-1980 (°C)
Figure 1.2.3. Increases in annual temperatures for a recent five-year period, relative to 1951-1980. (June 2007). InUNEP/GRID-Arendal Maps and Graphics Library. Retrieved 20:14, May 5, 2011 from http://maps.
grida.no/go/graphic/increases-in-annual-temperatures-for-a-recent-five-year-period-relative-to-1951-1980, credit to Hugo Ahlenius, UNEP/GRID-Arendal (Hansen, J., Sato, M., Ruedy, R., Lo, K., Lea, D.W. and Medina-Elizade, M. (2006). Global temperature change. Proc. Natl. Acad. Sci., 103, 14288-14293
Climate 13
Finally, the best examples of zoonotic disease spread as a partial result of climate changes are cholera and malaria. Cholera had almost disappeared, remaining endemic mainly in India, Pakistan and China;
nevertheless, since 1960 it has reemerged worldwide in the last five decades (Figure 1.2.4). As this disease is connected to water and poverty conditions (see chapter 1.4 and chapter 1.1), increasing floods due to climate changes between dry periods (e.g., El Niño and its consequences in South America and other regions) support the emergence of cholera. The second best example is malaria (Plasmodium falciparum) that is connected to one of the major climate forcings: CO2 atmospheric rise. The malaria parasite is transmitted by mosquito’ vectors to humans and mosquitoes in turn are impacted by CO2
concentrations that according to different models will increase in certain geographic areas, therefore increasing the vectors’ natural distribution (Figure 1.2.5). Among the endless reports on reemerging zoonotic diseases connected to so many factors, including climate change, it should be emphasized also that warming (the main trend in climatology) could affect the various pathogens in a different way (bacteria will react differently from viruses or parasites or helminthes) and therefore it is not an easy task to conclude in general terms, and some reservations should be considered before major conclusions (Randolph, 2010).
1950-1960 1960-1970
1970-1990 1990-2004
1 30 100 1 000 10 000 100 000
Nombre de cas de choléra déclaré par pays Source : Groupe de travail II et III, Rapport de synthèse du
GIEC, 2007.
/
Environmental Aspects of Zoonotic Diseases 14
1.2.1 REFERENCES
Berger, W.H., Schulz, M. & Wefer, G. (2010) Quaternary oceans and climate change: lessons for the future?Int J Earth Sci (Geol Rundsch)99, S171–S189.
Campino L. & Maia, C. (2010) Epidemiology of leishmaniases in Portugal.Acta Med Port23, 859–864.
Clement, J., Vercauteren, J., Verstraeten, W.W., Ducoffre, G., Barrios, J.M.et al.(2009) Relating increasing hantavirus incidences to the changing climate: the mast connection.Int J Health Geogr8, 1.
Desai, S., van Treeck, U., Lierz, M., Espelage, W., Zota, L.et al.(2009) Resurgence of field fever in a temperate country:
an epidemic of leptospirosis among seasonal strawberry harvesters in Germany in 2007.Clin. Infect. Dis.48, 691–697.
Kirilenko, A.P. & Sedjo, R.A. (2007) Climate change impacts on forestry. Proc. Natl. Acad. Sci. U.S.A. 104, 19697–19702.
Vorou, R., Pierroutsakos, I.N. & Maltezou, H.C. (2007) Crimean-Congo hemorrhagic fever.Curr. Opin. Infect. Dis.20, 495–500.
Randolph, S.E. (2010) To what extent has climate change contributed to the recent epidemiology of tick-borne diseases?
Vet. Parasitol.167, 92–94.
Figure 1.2.5. Climate change and malaria, scenario for 2050. (2005). InUNEP/GRID-Arendal Maps and Graphics Library. Retrieved 15:36, May 7, 2011 from http://maps.grida.no/go/graphic/ climate-change-and-malaria-scenario-for-2050, credit to Hugo Ahlenius, UNEP/GRID-Arendal (Rogers & Randolph. The Global Spread of Malaria in a Future, Warmer World. Science (2000:1763-1766)
Climate 15