Regime Shifts DataBase

Large persistent changes in ecosystem services

Between 1845 and 1850, a potato blight triggered a famine that killed or displaced 25% of the Irish population.  In Ireland, a host of economic, demographic, and social pressures marked the decades leading to the famine and meant that the Irish peasantry had no food options when the potato crop failed. The agro-ecosystem that developed in Ireland prior to the famine had characteristics typical of vulnerable environments: fields were close together, biodiversity was low, and a large amount of biomass made this ecosystem attractive to opportunistic pests. 

Nutrient and flow management. Management potentially stuck in a rigidity trap - no new ideas are able to take hold, due to vested capital and power dynamics.

Grand Canyon/Colorado River - Dam caused a large regime shift in ecology, but over time management has been adapted to try to approximate the original regime through water releases etc. Learnign how to do this has been achieved through experimentation & adaptive management.

Aquaculture growth has led to worries about overfishing and reduction in wild-caught food fish supply because of increased demand for fish meal. As such, the price ratio between fish meal and soybean meal has received much attention as an indicator of changing market conditions. In recent years, the price ratio between these two commodities has become more volatile. Several authors have suggested that the traditional relationship between fish meal and soybean meal has broken down and that this is evidence of increased demand pressure on fish meal. In this article, we investigate the hypothesis that there are two regimes for the relative price between fish meal and soybean meal. The empirical results support this hypothesis, with the low-price regime representing the traditional stable relative price. The continued linkages between the fish meal and the soybean meal markets indicate that aquaculture is reducing its dependency on marine proteins in favour of vegetable proteins.

Around 85% of the native woodland and forest cover has been removed from the mid catchment of the Goulburn-Broken, and 98% from the lower catchment (GBCMA 2003). Anderies et al. (2006b) estimate that the cover of woody vegetation was reduced to below the threshold level needed to maintain the water table below the surface about a decade after clearing began. This threshold is estimated at about 80% vegetation cover in the mid catchment (groundwater in the upper catchment appears not to be connected to water tables in the mid and lower catchment). As water tables rise in response to the reduced vegetation cover, there is a critical threshold at around 2 m below the surface (depending on soil texture). When the water table rises above this, capillary action draws water to the surface. The height of the water table determines the area salinized because of topographic variation, so area salinized and water-table depth are treated as a single threshold. Because of a strong hysteresis effect (tree roots do not function well in saturated soil, so it takes more trees than in unsaturated soil to achieve the same amount of transpiration), more than 80% of the catchment needs to be revegetated to change the trajectory of the system such that the equilibrium water-table depth is below the root zone. As this would affect large areas of dryland farms, pumping is needed in addition to revegetation—the less revegetation, the more pumping (see Anderies et al. 2006b). A constraint is the large volumes of saline water produced. Almost twice as much saline water needs to be pumped if there is no revegetation, which would violate the current salt discharge cap. Revegetation and pumping are both costly. Extracted from Walker et al 2009.

What they found was a remarkable global consistency between access to fish and seabird breeding success. Wherever they occurred in the world the effect of low fish was similar. Österblom and his colleagues found that breeding reaches a plateau and does not change even as food abundance increases. When the amount of fish in the sea was greater than one-third of maximum levels of fish, the number of chicks produced remained pretty much unaffected. But if the fish abundance fell below this one-threshold, the number of chicks produced declined. "The global pattern shows a threshold below which the numerical breeding response declines strongly as food abundance decreases," says Henrik Österblom. Österblom and his colleagues also found that breeding reaches a plateau and does not change even as food abundance increases.