By Jan Pokorný
Keywords: solar energy, plant evaporation, water cycles, climate, landscape management
Humans existed on Earth as hunters and gatherers for hundreds of thousands of years and the carrying capacity of a forest is one to three persons per square kilometre. But the civilizations, characterized by agricultural overproduction to supply cities and armies, developed in the last ten thousand years, dried out their environments; archaeologists find their relics buried under sand. Population growth led to the conversion of forest into agricultural land. Crop plants such as grains, corn, and potatoes did not tolerate floods, so farmers would drain wetlands and fields. Rainwater was also collected and drained from towns. The old civilizations of Mesopotamia, Indus Valley, the South American Incas, and North Africa did not burn fossil fuels increasing the carbon dioxide concentration in the atmosphere; rather, they collapsed due to lack of precipitation and high salinity of soil. It was bad management of land and water that led to soil fertility loss, droughts, and sandstorms. Industrialization would introduce further anthropogenic disturbances.
The UN Conference on Climate Change 2015 in Paris (COP21) set a goal for limiting global warming at less than 2OC of global average temperature (GAT) compared to pre-industrial levels. According to the Intergovernmental Panel on Climate Change (IPCC), the quantifiable criterion of climate change is GAT and the reason for global warming is increasing greenhouse gas (GHG) concentrations, particularly CO2 and CH4.Water vapour is considered only as a passive ‘feedback agent’, rather than an active agent of climate change. The IPCC minimizes water and land cover as controlling factors of climate, yet the amount of water vapour in the air is one to two orders of magnitude greater than that of CO2 and CH4.Water vapour forms clouds, which prevent the passage of solar energy to Earth, reducing temperatures substantially. The transition between the three phases of water – liquid, solid, and gaseous – is linked to heat energy. But landscape management patterns – deforestation, wetland drainage, urban soil sealing – change the distribution of solar energy such that it cannot be used in the cooling process of atmospheric water evaporation.
On a sunny day up to 1000W of solar energy falls on each square metre of Earth. Dry land, city surfaces – roofs, road asphalt, pavements – will heat to about 60OC, whereas beneath tree shade temperatures do not go over 30OC. About 50 per cent of wetlands were drained in the USA (45.9 million ha) releasing a huge amount of heat into the atmosphere. A tree also actively cools itself and its environment by evaporation of water. A tree supplied with water is an air-conditioning system driven by solar energy. Solar energy is hidden or latent in water vapour and is released in cool places as water vapour precipitates back into liquid water. The tree equalizes temperature gradients in a double way. It cools through evaporation and heats through condensation. Technological air-conditioning is flawed in comparison with vegetation: first, because it depends on polluting electricity generation; and second, even while it cools inside a room it releases heat outside, so
increasing the surrounding temperature.
Conventional analyses of global warming, such as those offered by the IPCC, typify what can be called the Old Water Paradigm. This treats global warming impacts on the water cycle rather than examining water as an active determinant of climate. The Old Water Paradigm assumes the following:
• The increase of global average temperature is the main climatic problem
• The mitigation via decrease of GHGs can perhaps be expected within a horizon of centuries
• Drainage and the urban landscape have a minimal impact on the water cycle
• Water vapour acts as a GHG causing higher temperatures
• Vegetation has low albedo or solar reflectance capacity and so increases greenhouse effects
The New Water Paradigm described in the book Water for Recovery of Climate (Kravþík et al. 2008) treats water as the medium equalizing temperature differences in time and space, between day and night, here and there. The assumptions are the following:
• Extremes of weather, erratic drought, and cyclonic storms are the main climatic problem
• Deforestation, large-scale agriculture, and urbanization change the local water cycle, which, in turn, impacts global atmospheric weather patterns
• Transpiring vegetation alleviates air temperatures, cloudiness moderates the intensity of solar radiation coming to the Earth’s surface
• Water vapour condenses by night and prevents infra-red radiation (IR) moving from the Earth’s surface towards the sky
• With a new approach to water management, a possible recovery of the climate can be expected within decades.
New Water Paradigm principles have been demonstrated in Australia by Peter Andrews’ method of Natural Sequence Farming. This emulates the role of natural water courses to reverse salinity, slow erosion, and increase soil and water quality, recharge subterranean aquifers, and enables native vegetation to restore the riparian zone. In India, the Tarun Bharat Sangh project pioneered by Rajendra Singh is based on the revival of traditional water reservoirs. The work is aimed at designing water harvesting structures or johads. These are simple, mud barriers built across hill slopes to arrest monsoon runoff. The height of the embankment varies depending on site, water flow and topography. A johad holds water for livestock and allows water percolation down through the soil, recharging the aquifer as far as a kilometre away. This water harvesting has irrigated an estimated 140,000 hectares and increased the water table from about 100–20 metre in depth to 3–13 metre. Crop yields have highly improved. Forest cover has gone from 7 per cent to 40 per cent. More than 5,000 johads were built all together and over 2,500 old structures rejuvenated by village communities in 1,058 villages since 1985. Similar projects in Slovakia have created employment opportunities and enhanced the sense of community.
Andrews, Peter (2006), Back from the Brink: How Australia´s Landscape Can Be Saved. Sydney: ABC Books.
Kravþík, Michal, Jan Pokorný, Juraj Kohutiar, Martin Kováþ and Eugen Tóth (2008), Water for the Recovery of Climate: A New Water Paradigm, www.waterparadigm.org.
Makarieva, Anastassia, and Viktor Gorshkov (2007), ‘Biotic Pump of Atmospheric Moisture as Driver of the Hydrological Cycle on Land’, Hydrol: Earth Syst. Sci.11:1013–33, 10.5194/hess-11-1013-2007.
Pokorný, Jan, Petra Hesslerová, Hanna Huryna, and David Harper (2016),‘Indirect and Direct Thermodynamic Effects of Wetland Ecosystems on Climate’ in Jan Vymazal (ed.), Natural and Constructed Wetlands: Nutrients, heavy metals and energy cycling, and flow. Zurich: Springer.
Ponting, Clive (1991), A Green History of the World: The Environment and the Collapse of Great Civilizations. London: Penguin.
Schneider, Eric and Dorion Sagan (2005), Into the Cool, Energy Flow, Thermodynamics, and Life. Chicago: University of Chicago Press.
Jan Pokorný is a plant physiologist who graduated from the Charles University, Prague. He has researched the photosynthesis of wetland plants with the Czechoslovak Academy of Sciences and the CSIRO, Australia. Since 1998, he is Director of the research organization ENKI, dealing with the direct role of landscape conditions and plant activity in the distribution and interaction of solar energy, water cycles, and climatic effects.
Essay originally published in Pluriverse: A Post-Development Dictionary (Edited by Ashish Kothari, Ariel Salleh, Arturo Escobar, Federico Demaria, and Alberto Acosta)
Published with kind permission of the authors.