I have a question regarding how the different ecosystem services are quantified and then compared to each other. For example, if there is a trade-off between pollinators and crops, how is it quantified? What equation is used in order to unify values in order to compare the different services?
Hello @clara_ur and welcome to the forums!
As of the current release of InVEST, version 3.13, there isn’t a single unified metric across all of the models, but you could conceivably link service provision to some other metric that would give you this sort of comparison. Most applications that the Natural Capital Project team has worked on (that I am aware of) typically tries to treat each service individually. So if you’re aiming for an optimization solution, your objective function might be “maximize crop yields while also minimizing nutrient runoff” or something like that, which doesn’t reduce the ecosystem services metrics to a single number.
For the specific example you gave, I’d suggest looking at the pollination model’s yield outputs and seeing if that might directly answer your question.
Many versions ago, InVEST used to offer valuation components that would put a monetary value on the services modeled. These were removed for a variety of reasons, including that there are many forms of value, and so reducing an ecosystem service to just one metric is generally misleading and reductive.
I hope I’m representing the above accurately and I’d love any extra input, corrections or clarifications here from @swolny, @jesseG or anyone else!
James
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HI @clara_ur -
One thing we do is identify “hotspots” of service provision across several services. To do this, we’ll select the pixels with the top, say, 20% of values for each service, then see which pixels fall within the top 20% of 1, 2, 3 or however many services you’re considering. The resulting map would show which pixels provide the most service across the largest number of services.
You could also normalize the different service values, if you want to compare them more directly.
~ Stacie
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I would add that we don’t typically look to combine results from different InVEST models without knowing more about the values and issues in the region of interest. For instance, sediment retention may be more valuable to communities that obtain their drinking water from local creeks than it is to those that use groundwater. Coastal risk reduction is only of interest to coastal communities. So, it is up to the user to determine how to weight the different impacts based on the realities of the study area, the types of ecosystems that are there, and the values of the communities that live there.
-Jesse
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