Monitoring Changes in Ecosystem Services

Hello all!

In my previous post, I concluded the examples of both monetary and non-monetary valuations of ecosystem services for the environmental policy-making. Although the referred reading is filled with mathematical jargon, I hope to provide a brief and comprehensible summary on how mapping and modeling approaches can be used to quantify biophysical changes in ecosystem services, which are beneficial to management scenarios in consideration of future changes. They combine ecosystem service analyses with the emerging field on Geographic Information Systems (GIS), both of which are emerging academic fields in their own right.

Ecosystem services change in West Africa (Leh et al. 2013)

Tools such as the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) tool (Tallis et al. 2011) were used to quantify individual ecosystem services – selecting and quantifying for biodiversity, surface water yield, carbon storage, sediment retention, nitrogen retention and phosphorus retention across 40 hydrological basins in both Ghana and Cote d’Ivoire. These were run using previously published literature on the formulae deriving each ecosystem service (FAO, 2004; Tallis et al. 2011; Wischmeier and Smith, 1978; Woomer et al. 2004; Hassan et al. 2005).

These indices were standardized across all 40 basins for comparison and subsequently combined in the study to provide an overall value of the ecosystem status, and GIS analysis through remote sensing was subsequently carried out to visualize ecosystem changes at the basin and sub-basin scales from changing land use.

Figure 5. Map representation of Ecosystem Services Status Index (ESSI) for the numbered hydrological basins in Ghana and Cote d’Ivoire.

Figure 6. Basin-scale Ecosystem Services Change Index over time relative to 2000, for the 40 numbered major hydrologic basins in Ghana and Cote d’Ivoire.

The ESSI allows us to first prioritise the location of these services by identifying which basin has shown the most negative impacts, and subsequently the ESCI allows for us to identify which individual ecosystems services have been depleting to prioritise for mitigation and conservation. The ESSI values for basin 10 in both 2005 and 2009 indicate critical danger with about 38% loss in total number of ecosystem services analysed relative to 2000 as seen in Figure 5. The ESCI supplements this understanding to identify which services ought to be given extra attention, for example in basin 10 biodiversity and water yield should be targeted since there is a loss of 63% and 19% of services respectively relative to 2000 conditions seen in Figure 6. These two highlighted figures are often in synergy - biodiversity loss can often be linked to losses in water yield, or vice versa. They provide quick and essential information required for the management of ecosystem services.

The study was one of the first studies in data scarce West Africa on mapping multiple ecosystem services statuses at the basin scale. Modelling and mapping these ecosystem statuses allows for the cumulative impression of all activities on ecosystem health, especially in response to changing land use. Overall, there was a general decrease in ecosystem services from 2000 to 2009. Such findings could be simulated for areas with better geospatial information, where future scenarios of land use could be modeled to identify for the losses in ecosystem services. Nonetheless, caution is necessary in interpreting these simulations, as they are sensitive to the geographic resolution and choice of ecosystem services, as different sets of ecosystem services would see significantly different results from the trade-offs between ecosystem services.

In this post, I have mostly spoken about how geographical information systems may be paired with an ecosystem services approach to identify impacts of changing land use, with a case study focus on data scarce West Africa. In my next post, I would speak more about an ecosystem service approach in the face of future climate change, and the impending threats to livelihoods.

See you!