Vulnerability of Latin America to Climate Change and Climate Variability

which, according to several historians, was a gradual process that could have lasted for about 200 years.

These coincidences have led some advocates of the climate catastrophe thesis to emphasize the role of droughts in triggering the decline of the Mayan civilization. Despite the undeniable contribution of these extreme hydrometeorological events, other archaelogical hints display a much more complex history. In fact, there is enough evidence to suggest that the decline of the Mayan civilization underwent different processes in the mountain highlands associated than in the north and south of the Yucatan lowlands. The decline of the Mayan civilization was an extremely complex, multifactorial, and heterogeneous process in time and space. This process started during the Classic period, continued through the post Classic period, and lasted until Nojpetén, the last pre-Columbian Mayan site in Lake Peten, succumbed in 1697, many years after the conquest began with the arrival of the Spaniards.

Indeed, the complexity of this process lends credibility to the theory that several factors were involved, and a number of continuous droughts triggered the decline of the Mayan civilization. Even though this integrationist hypothesis is reinforced by several data, it would be better to focus on the specific relevance of each factor in individual sites before generalizing. Some of these clues come from scientific fields that we would never suspect, such as hydrological and dynamic modeling.

Using several models, we may simulate the evolution timeline of the Mayan society fairly well, even with positive coincidences in the period in which intensive agriculture started to be practiced and the Mayan society flourished. One of these results reveals that even without droughts, the Mayans would have faced serious soil depletion problems owing to the widespread practice of intensive agriculture, which was required to feed the growing population that inhabited the large cities of the Classic period. A decreasing capacity in food production always results in malnutrition, diseases, and social discomfort, which could aggravate existing public health conditions due to overcrowding and decreasing public hygiene. In fact, this seems to have happened at least in two important Classic period sites, Copán and Palenque.

In other cases such as Palenque (Lakam ha’), hydrological simulations in the basin around the city suggest that droughts did not exert a significant impact on their water resources. However, land use changes seem to have altered the impacts from climate changes on the basin, perhaps increasing its sensitivity to droughts as denoted by climate reconstructions. In this case, we would have to look for other concomitant causes, probably of a sociopolitical nature, to completely explain the abandonment of this site since archaeological studies suggest that the deterioration of the environment and decrease in natural resources do not seem to have played a significant role on Palenque’s final decline.

One site for which much information is available is Tikal (Figure 1). In this city there were several reservoirs and a system of channels that helped the Mayans collect water for a number of uses. Although the quantities stored do not seem to have been enough for irrigating the entire agricultural area needed to feed all of the city’s inhabitants with corn, the contents of some peripheral reservoirs do seem to have been used for this purpose on some occasions. Even when the total amount of water could not have irrigated all crops, it does seem that a year of intense drought may not have brought many water supply issues, at least for public use, as it may be observed in urban demand modeling studies. Despite these conclusions, it is reasonable to assume that periods of recurrent drought may have limited water resources far beyond what was previously anticipated.

Another specific event that worsened the situation of Tikal was the contamination of the water reservoirs. By analyzing the sediment deposits, the presence of mercury was detected in the sediments of two of the main reservoirs located in the central area, where the main palaces, temples, and squares were located. Mercury came from cinnabar (mercury sulfide), an ore widely used for prepering the red colorant used in ceramics, buildings, and ritual practices such as burials.

Similarly, an increase of phosphate concentrations was detected in these reservoirs during the above mentioned periods, which, coupled with high temperatures and decrease in water supplies as a result of droughts, favored the proliferation of cyanobacteria. In addition to the above, a genetic material from Plantothrix and Microcystis and two cyanotoxin-producing genera were also found. These substances can be toxic at low concentrations (2 nM), and some of them are resistant to cooking. All these elements were found in sediment layers corresponding to the Late Classic and Terminal Classic periods.

The recurrent droughts came at a crucial time. The Mayan leaders of that period were increasingly cutting down a large

Figure. 1: Great Plaza and Pyramid, Tikal

number of the surrounding forests to devote those lands to intensive farming and producing the food required to feed growing populations. All this led to excessive deforestation, loss of vegetation cover, and ultimately, erosion and soil degradation. The land, dry and exhausted, ceased to cultivate. The water storages that came from the Chaac’s pitchers diminished and became poisonous and famine bloomed. The kings had lost the favor of the gods. From the wars that once brought wealth, prisoners, glory, and power, only exhaustion remained the end. This dramatic and overloaded image could have happened in Tikal more than a thousand years ago, but it would be unwise to think that it could not happen again. Today’s world moves with an extremely consumption-oriented socioeconomic model that has been sustained by excessive consumption of many natural resources; destruction of ecosystems; and pollution of soil, water, and air, leading to the exploitation and death of many of our own kind. Because of anthropogenic climate changes, an increase in extreme hydrometeorological events is predicted, especially droughts. This will occur in a technological world but the one ridden with poverty and millions of dissatisfied and vulnerable human beings.

As a society, society, we still have time to remember the wisdom and humaneness remaining whitin us. We can still see ourselves in the mirror of the ancient Mayans, peek into the sacred sink hole, and see in the depleted surface of the waters, unavoidably, coming from no far, the torch of Chaac.