Nature, Culture, and Conservation in the Anthropocene - Biodiversity Conservation and Environmental Change - page 148

What emerges from the study of adaptive cycles is that collapse and reorganization can
occur if critical combinations of environmental change, disease, social upheaval, and
political unrest combine (Redman and Kinzig 2003, Costanza et al. 2007). Such factors are
interlinked; droughts and other environmental shocks can strain food production and
water supply, with impacts on health, but will also lead to stress on social and institutional
systems, leading to political instability. Other examples from the long-term records high-
light the importance of water provision and food security in the sustainability of socio-
ecological systems. For example, Redman and Kinzig (2003) observed adaptive cycles in
Hohokam settlements of the lowland river valleys in the desert region of central and
southern Arizona, USA (c. 400-1400 ce). Their persistence in this arid environment is tes-
tament to effective irrigation systems, which directed water from the Salt and Gila Rivers
along canals that brought water and sediments to cultivated fields (Redman and Kinzig
2003). Stable annual stream flows from 700-1150 ce, enabled a feedback between growing
population and the expansion of irrigation systems, which Redman and colleagues sug-
gest constitutes the building phase of the adaptive cycle. From 1150-1400 ce, water-flows
were more erratic, and this stressed irrigation and food production systems. This led to
reorganization of resource management, and eventually to the collapse of Hohokam soci-
ety at 1400 ce in the release and revolt phase of the adaptive cycle (Redman and Kinzig
2003). More recently, an environmental tipping point was reached in the south of France
in the nineteenth century, where degradation of mountain areas was triggered by popula-
tion growth, which led to ploughing and cultivation in marginal areas for subsistence
farming. The degradation trend was reversed in the mid nineteenth century, when farmers
shifted to livestock production for national markets. As a result, the area of land under
cultivation decreased and landscapes became mosaics of forests and pasture. In the late
twentieth century, demand for sheep products declined and many farms were abandoned,
enabling the expansion of forest cover and the loss of pasture and meadow habitats (Taille-
fumier and Piégay 2003).
It seems likely that patchy, heterogeneous landscapes are more resilient to environmental
change. Spatial resilience can be fostered by ensuring that landscape management main-
tains heterogeneity and is carried out over scales that allow regenerative processes to oper-
ate; a landscape is considered sustainable if it has the capacity to regenerate (Cumming 2011,
Cumming et al. 2013). Therefore the landscape itself and the scales of management interven-
tion must be in accordance with ecological processes like forest patch dynamics (see Chap-
ter 4) (Cumming 2011, Cumming et al. 2013, Turner et al. 2013). Land abandonment can lead
to simplification of spatial structure and loss of biodiversity, as mosaic landscapes become
homogenized by returning tree cover with the loss of habitat for light and disturbance
adapted taxa (see Chapters 4 and 6) (Agnoletti 2007, Feurdean 2010, Shakesby 2011). Too little
or too much disturbance can homogenize landscapes, but intermediate levels of disturbance
maintain a range of habitat types and associated ecosystem services, and it seems likely that
resilience and adaptive capacity are highest when heterogeneous, multifunctional land-
scape mosaics are maintained (Antrop 2005, Cumming 2011, Cumming et al. 2013). Further-
more, such landscapes foster significant cultural, social, and aesthetic benefits, as well as