Ecosystem service provision sets the pace for pre-Hispanic societal development in the central Andes

Evidence for change in societal organization

Archaeological records reveal three major states of pre-Hispanic societal organization around Lake Titicaca during the last 5000 years: (1) mobile populations engaged in hunting and foraging (before 3750 yr BP), (2) at least partially settled populations organized into village groupings with trade links and agricultural activity (c. 3250–2750 yr BP) and (3) urban centres containing complex social, political and religious structures often termed ‘civilizations’ (c. 2500 yr BP onwards) (Aldenderfer, 1998; Stanish, 2011). The transition from mobile hunter–foragers to more sedentary communities is evident in the archaeological record from the appearance of at least semi-permanent settlement sites at Chiripa, Pucara and Taraco (Figure 2) from c. 3350 yr BP (Figure 3B(b)–(d)). The settled populations are closely associated with extended human capability to modify the environment at a landscape scale, for example, widespread implementation of basic irrigation systems, Quinoa cultivation and crude pottery (Figure 3A(b)–(e)). Regional political organization is indicated from c. 2500 yr BP with the growth of a settlement at Chiripa and the widespread presence of complex storage, residential and religious structures (Stanish, 2011). The first evidence of the site of Tiwanaku (Figure 2) becoming a regional focal point dates from c. 2200 yr BP (Figure 3E). Within a few centuries of the foundation of Tiwanaku, the settlements at Chiripa, Taraco and Pucara declined while Tiwanaku continued to grow and reached a maximum population of 30,000–60,000 people c. 1200–950 years ago (Figure 3B(e)). During the period of maximum population at Tiwanaku, technological and agricultural practices were developed, including intensification of camelid pastoralism, commencement of silver mining, raised bed agriculture and integrated flood and irrigation systems (Figure 3A(f)–(i)). The gradual decline of Tiwanaku (c. 950–850 yr BP) saw power transfer into four regional polities (Figure 3B(f)–(i)), which developed new styles of monumental, funereal and defensive structures (Figure 3A(j) and (k)). Subsequently, external rule was imposed by the Inka from c. 580–530 yr BP (Figure 3B(j)) and later the Spaniards in ad 1532 (Rowe, 1946).

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Figure 3.

Societal development and natural resource provision in the Lake Titicaca region over the last 5000 years.

Evidence for change in ecosystem service provision

Past environmental change records allow the reconstruction of the pattern of change in ecosystem service provision which have accompanied the last 5000 years of societal change. The availability of water resources in the central Andes is recorded by markers within ice and lake sediment cores, which reflect change at different spatial scales. Around 5000 years ago, the Andes emerged from a multimillennial period characterized by increased drought frequency. This mid-Holocene dry event has been recognized across the central Andes (Bush and Gosling, 2012). Following the end of the mid-Holocene dry event, the Lake Titicaca region became, on the landscape scale, gradually wetter (Figure 3C(a) and (b)). However, lake sediments which record changes in water-level formed in the wider region (Lakes Huiñiamarca and Challacaba; Figure 2) indicate that variation in moisture balance was spatially heterogeneous on 100–1000 year timescales (Figure 3C(c) and (d)). Fossil pollen records obtained from lake sediments indicate that, at a landscape scale, the amount of Polylepis woodland within the grassland-dominated landscape varied naturally in extent prior to the arrival of humans > 8000 years ago (Dillehay, 2008; Erickson, 2000; Gosling et al., 2009). Between 5000 and 2000 years ago, Polylepis pollen constituted c. 8% of the total terrestrial pollen inputting into Lake Titicaca, but after 2000 yr BP, this figure rarely reaches above 2%. High elevation (>4000 m above sea level) sites to the northeast (Katantica, Cotapampa and Amarete) and southeast (Chacalataya, Cumbre Unduavi and Rio Kaluyo) of the Titicaca basin do not record Polylepis as present during the last 5000 years (Graf, 1992) (Figure 2), while to the south, there is evidence of the persistence of Polylepis in the landscape for the entirety of the last 5000 years (Figure 3D(c)–(e)).

Abundant resources and settled society

The end of the mid-Holocene dry event is marked by the rise in Lake Titicaca water-level from 5000 years ago (Figure 3C(b)), and the inception of Lake Challacaba at c. 4300 yr BP (Figure 3C(d)). The increased moisture availability coincides with the cultural transition from mobile hunter–foragers to more sedentary populations, which were organized into coalitions of villages (Figure 3B(c) and (d)) (Stanish, 2011). The increase in local fire activity within this period of ‘wetter’ climatic conditions (Williams et al., 2011) strongly suggests that populations close to lakes were expanding, that is, collecting, transporting and burning increasing amounts of wood (Figure 3D(b)). However, the transition to more settled populations does not appear to have had a long-term detrimental impact on the woodland resources (Figure 3D(a)) despite clear evidence of larger human populations (proliferation of villages) and increased resource use (buildings and charcoal). After 1000 years of relative cultural stability, around 2250 years ago, villages at Chiripa and Taraco began to expand and the settlement at Tiwanaku was founded (Figure 3B(b), (d) and (e)). The change in societal organization marked the establishment of the first regional-scale political organization or ‘civilization’ (Stanish, 2011).

Scarce resources, technological innovation and centralization of societal organization

The reduced availability of water and woodland resources in the Lake Titicaca region from c. 2250–1750 yr BP spans a period which saw the gradual emergence of Tiwanaku as a consolidated single regional urban centre for societal organization. As Tiwanaku developed, people diversified their economic activity and improved their use of the landscape, for example, commencement of silver mining and advent of raised bed agriculture (Figure 3A(g)–(i)). The reduction in water availability from c. 2200 yr BP is likely to have been driven by external climate factors (Bush and Gosling, 2012). However, the decrease in woodland resources close to Lake Titicaca (Figure 3D(a)), but not in the surrounding region (Figure 3D(c)–(e)), supports the suggestion that exploitation by the human population close to the lake was the likely cause for locally reduced woodland (Paduano et al., 2003).

The gradual loss of both water and woodland ecosystem service provision is broadly coincident with the consolidation of disparate village-based populations into the more substantial urban centre at Tiwanaku (Figure 3B(e)). Due to uncertainties inherent with chronologies of the archaeological and past environmental change data, it is not possible to directly attribute specific decreases in resource availability as a ‘trigger’ which instigated societal change. However, it seems likely that the landscape scale (10–100 km) changes to baseline resources, as indicated from the past environmental change record, would have impacted the trajectory of societal change (100–1000 years), as suggested by the archaeological record, because of the population’s reliance on environmental resources. In addition, it seems plausible that the underlying environmental pressure could also, in part, have influenced the need, or desire, for people to diversify resource use (i.e. silver mining) and develop new agricultural practice (i.e. raised bed agriculture).

Increased water resource and regionalization of societal power

The positive accumulation balance for the Sajama ice core and deepening of Lake Challacaba indicate that regionally, the water balance started to increase again around 1000 yr BP (Figure 3C(a) and (d)). Almost immediately, there was an increase in regional camelid herding (Figure 3D(g)) as the site of Tiwanaku and its distal influence expanded to its maximum (Figure 3B(e)). The rapid expansion of Tiwanaku suggests that the ephemeral societal structures that had developed during the preceding arid period meant that people were well placed to take advantage of increased water availability despite there being no recovery in woodland resources close to the lake (Figure 3D(a)). After almost 1000 years as a significant centre of civilization in the central Andean highlands, Tiwanaku began to gradually decline around 900 years ago and was replaced by numerous regional polities (Figure 3B(f)–(i)). The decline of Tiwanaku has been previously linked to both climatic (Binford et al., 1997; Ortloff and Kolata, 1993) and societal pressures (Kolata, 1986). The information collated here is not at a sufficient temporal resolution to comment on the nature of any specific trigger for the decline of Tiwanaku; however, the environmental data suggest that the transition occurred within the context of a general increase in regional water resource availability.

Abundant resource attracts inward migration

Societies in the Lake Titicaca region were altered c. 580–530 years ago with the arrival of the Inka (Figure 3B(j)) who imposed an external control over the populations (Hastorf, 2003; Rowe, 1946). The desire for extra-regional Andean peoples to control the Lake Titicaca region indicates the presence of valuable resources. During the Inka period, the Titicaca region remained an important regional centre within the empire, became part of an increasingly complex inter-connected Andean society (Stanish, 2011), and the more peripheral Cochabamba region (Lake Challacaba) became one of the centres for maize production (La Lone and La Lone, 1987). The brief period between the arrival of the Inka and Europeans in ad 1532 means that it is difficult to assess the relationship between Inka-led society and ecosystem service provision. However, the continued population expansion (La Lone and La Lone, 1987) and extensive trade linkages (Knudson et al., 2012) suggest that the peoples of the Lake Titicaca region continued to successfully manage the natural resources available.

Long-term (>100 year) patterns of change in societal organization and ecosystem services

The spatial and temporal disparity between the archaeological and past environmental change records considered places a fundamental limit on the inferences that can be drawn, for example, we acknowledge that there is uncertainty in the dating control on many of the archaeological data (Figure 3A and B). In an attempt to negate these concerns, we focus on larger spatial and longer timescales (i.e. upper right portion of Figure 1) and discuss the larger/longer-term patterns of change rather than referring to specific events. To assess whether the sequence of change observed in the archaeological and past environmental change record follows any regular pattern, we will now consider the evidence presented within the context of ‘adaptive cycles’ (Gunderson and Holling, 2002). Adaptive cycles are an element within the wider concept of ‘resilience theory’ designed to aid understanding of ecosystems, agencies and people, based upon potential, connectivity and resilience within a landscape (Holling and Gunderson, 2002). The ‘potential’ of a landscape relates to the opportunities for change that are present, that is, are there resources present which can be better utilized or unlocked by a technological advance; the ‘connectivity’ relates to the degree of linkages within the systems and ‘resilience’ relates to the robustness of that system. As the amount of these various factors fluctuates within a system, a pattern of change occurs which can be summarized into four key states: (1) release or destabilization of a system allowing previously ‘locked up’ resources to be released (Ω), (2) renewal or reorganization when system undergoes change (α), (3) growth and exploitation as resources are easily accessed (r) and (4) conservation or maximum connectivity as systems peak and resources are locked up (K) (Gunderson and Holling, 2002; The Resilience Alliance, 2002). The use of the adaptive cycle’s framework provides a concise way of describing the long-term (>100 year) complex interactions between humans and the environment (Figure 4). In addition, the application of adaptive cycles to the record of past human and environmental change allows discussion to be placed in a language relevant to international policy development (Dearing, 2012).

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Figure 4.

Adaptive cycle loop showing connections between system states identified in the Lake Titicaca region (solid white arrows), and other potential conceptual connections (dashed white arrows).

The overall pattern of societal (Figure 3A and B) and ecosystem service (Figure 3C and D) development observed in the Lake Titicaca region during the last c. 5000 years show three repeated adaptive cycles (Figure 3E). Increased water resources c. 3400 yr BP saw the destabilization (Ω) of hunter–forager societies and their reorganization (α) into more sedentary village coalitions. The subsequent period of resource stability (water and woodland) resulted in growth (r) until a period of ‘maximum connectivity’ was achieved (K) and the first regional-scale political and societal organization in the central Andes was established (c. 2500 yr BP). The decline in woodland and water resources near Lake Titicaca c. 2200 yr BP resulted in another gradual destabilization (Ω) and reorganization (α) of societies. Societal organization was consolidated into one regional urban centre (Tiwanaku), activity within the landscape diversified and new methods for maximizing natural resource use were developed (r), despite low water and woodland resource availability. Technological advances and increasing water availability culminated in the growth of Tiwanaku to its maxima by c. 1000 yr BP (K). Increase in access to water resource regionally from c. 1000 yr BP destabilized the region again (Ω), facilitated a regionalization of power and attracted the Inka into the region (α).