IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

13.6 Case studies

Box 13.1. Amazonia: a ‘hotspot’ of the Earth system

The Amazon Basin contains the largest contiguous extent of tropical forest on Earth, almost 5.8 million km2 (see Figure 13.3). It harbours perhaps 20% of the planet’s plant and animal species. There is abundance of water resources and the Amazon River accounts for 18% of the freshwater input to the global oceans. Over the past 30 years almost 600,000 km2 have been deforested in Brazil alone (INPE-MMA, 2005a) due to the rapid development of Amazonia, making the region one of the ‘hotspots’ of global environmental change on the planet. Field studies carried out over the last 20 years clearly show local changes in water, energy, carbon and nutrient cycling, and in atmospheric composition, caused by deforestation, logging, forest fragmentation and biomass burning. The continuation of current trends shows that over 30% of the forest may be gone by 2050 (Alencar et al., 2004; Soares-Filho et al., 2006). In the last decade, research by the Large Scale Biosphere-Atmosphere (LBA) Experiment in Amazonia is uncovering novel features of the complex interaction between vegetated land surfaces and the atmosphere on many spatial and temporal scales. The LBA Experiment is producing new knowledge on the physical, chemical and biological functioning of Amazonia, its role for our planet, and the impacts on that functioning due to changes in climate and land use (http://lba.cptec.inpe.br/lba/site/).

There is observational evidence of sub-regional changes in surface energy budget, boundary layer cloudiness and regional changes in the lower troposphere radiative transfer due to biomass-burning aerosol loadings. The discovery of large numbers of cloud condensation nuclei (CCN) due to biomass burning has led to speculation about their possible direct and indirect roles in cloud formation and rainfall, possibly reducing dry-season rainfall (e.g., Andreae et al., 2004). During the rainy season, in contrast, there are very low amounts of CCN of biogenic origin and the Amazonian clouds show the characteristics of oceanic clouds. Carbon cycle studies of the LBA Experiment indicate that the Amazonian undisturbed forest may be a sink of carbon for about 100 to 400 Mt C/yr, roughly balancing CO2 emissions due to deforestation, biomass burning, and forest fragmentation of about 300 Mt C/yr (e.g., Ometto et al., 2005). On the other hand, the effect of deforestation and forest fragmentation is increasing the susceptibility of the forest to fires (Nepstad et al., 2004).

Observational evidence of changes in the hydrological cycle due to land-use change is inconclusive at present, although observations have shown reductions in streamflow and no change in rainfall for a large sub-basin, the Tocantins river basin (Costa et al., 2003). Modelling studies of large-scale deforestation indicate a probably drier and warmer post-deforestation climate (e.g., Nobre et al., 1991, among others). Reductions in regional rainfall might lead to atmospheric teleconnections affecting the climate of remote regions (Werth and Avissar, 2002). In sum, deforestation may lead to regional climate changes that would lead in turn to a ‘savannisation’ of Amazonia (Oyama and Nobre, 2003; Hutyra et al., 2005). That factor might be greatly amplified by global warming. The synergistic combination of both regional and global changes may severely affect the functioning of Amazonian ecosystems, resulting in large biome changes with catastrophic species disappearance (Nobre et al., 2005).

Box 13.2. Adaptation capacity of the South American highlands’ pre-Colombian communities

The subsistence of indigenous civilisations in the Americas relied on the resources cropped under the prevailing climate conditions around their settlements. In the highlands of today’s Latin America, one of the most critical limitations affecting development was, as currently is, the irregular distribution of water. This situation is the result of the particularities of the atmospheric processes and extremes, the rapid runoff in the deep valleys, and the changing soil conditions. The tropical Andes’ snowmelt was, as it still is, a reliable source of water. However, the streams run into the valleys within bounded water courses, bringing water only to certain locations. Moreover, valleys and foothills outside of the Cordillera Blanca glaciers and extent of the snow cover, as well as the Altiplano, receive little or no melt-water at all. Therefore, in large areas, human activities depended on seasonal rainfall. Consequently, the pre-Colombian communities developed different adaptive actions to satisfy their requirements. Today, the problem of achieving the necessary balance between water availability and demand is practically the same, although the scale might be different.

Under such limitations, from today’s Mexico to northern Chile and Argentina, the pre-Colombian civilisations developed the necessary capacity to adapt to the local environmental conditions. Such capacity involved their ability to solve some hydraulic problems and foresee climate variations and seasonal rain periods. On the engineering side, their developments included rainwater cropping, filtration and storage; the construction of surface and underground irrigation channels, including devices to measure the quantity of water stored (Figure 13.4) (Treacy, 1994; Wright and Valencia Zegarra, 2000; Caran and Nelly, 2006). They also were able to interconnect river basins from the Pacific and Atlantic watersheds, in the Cumbe valley and in Cajamarca (Burger, 1992).

Figure 13.4

Figure 13.4. Nasca (southern coast of Peru) system of water cropping for underground aqueducts and feeding the phreatic layers.

Other capacities were developed to foresee climate variations and seasonal rain periods, to organise their sowing schedules and to programme their yields (Orlove et al., 2000). These efforts enabled the subsistence of communities which, at the peak of the Inca civilisation, included some 10 million people in what is today Peru and Ecuador.

Their engineering capacities also enabled the rectification of river courses, as in the case of the Urubamba River, and the building of bridges, either hanging ones or with pillars cast in the river bed. They also used running water for leisure and worship purposes, as seen today in the ‘Baño del Inca’ (the spa of the Incas), fed from geothermal sources, and the ruins of a musical garden at Tampumacchay in the vicinity of Cusco (Cortazar, 1968). The priests of the Chavin culture used running water flowing within tubes bored into the structure of the temples in order to produce a sound like the roar of a jaguar; the jaguar being one of their deities (Burger, 1992). Water was also used to cut stone blocks for construction. As seen in Ollantaytambo, on the way to Machu Picchu, these stones were cut in regular geometric shapes by leaking water into cleverly made interstices and freezing it during the Altiplano night, reaching below zero temperatures. They also acquired the capacity to forecast climate variations, such as those from El Niño (Canziani and Mata, 2004), enabling the most convenient and opportune organisation of their foodstuff production. In short, they developed pioneering efforts to adapt to adverse local conditions and define sustainable development paths.

Today, under the vagaries of weather and climate, exacerbated by the increasing greenhouse effect and the rapid retreat of the glaciers (Carey, 2005; Bradley et al., 2006), it would be extremely useful to revisit and update such adaptation measures. Education and training of present community members on the knowledge and technical abilities of their ancestors would be the way forward. ECLAC’s procedures for the management of sustainable development (Dourojeanni, 2000), when considering the need to manage the extreme climate conditions in the highlands, refer back to the pre-Colombian irrigation strategies.