Hi @leonale ,
Thank you for writing in with your question.
This is a complicated question that I will not try to answer fully in one post, but instead I’ll at least provide a relatively short response to start. Of course, you should generate scenarios, such as by creating multiple input landcover maps, with one representing the current or baseline conditions and the others representing the landscape after the conservation activities are completed. Or perhaps it’s more appropriate to generate different biophysical table inputs with a baseline and then scenarios with altered values based on the activities. Without knowing the specifics of the conservation activities, it is difficult for me to guide you precisely on how to properly create the baseline versus conservation scenarios.
Once you have baseline and scenario results, you should compare them to explore the differences. Depending on the InVEST model, it may be appropriate to subtract the values of relevant output rasters (baseline sediment export minus sediment export after conservation activities, for example). The carbon model can compare scenarios for you in a single run, but the others require you to perform multiple runs yourself and manually compare the results.
Next, the process of translating the differences in services under different scenarios into value becomes less straight forward and really depends on knowing the specifics of your study area. Typically, we start by determining who the beneficiaries are of the services. For instance, when looking at any of the water model results, how many people live downstream that would be affected? Valuation can take many forms besides monetary, and affected population is certainly one measure of value. Spatial population data can by used to identify cities or towns. InVEST comes with an additional tool called DelineateIt that uses an input DEM and vector inputs representing stream intake points, population centers, roads, municipal boundaries, or other features of interest in order to define upstream areas to use in aggregating services provided to beneficiaries. Another example for water models that we often use is looking at how reservoirs might be affected by changes in sedimentation rates.
It is important to research how resources are used and valued in your study region. Do people use surface water for drinking? Who benefits locally from biodiversity and how? Is ecotourism important in the area, or timber harvesting, or both, neither, something else? Of course, we all benefit from reduced carbon emissions, no matter where on the planet the change occurs.
I could go on, but please consider these ideas and be sure to do your due diligence in researching how resources are used in your region of interest, and by whom, to help determine whom the services benefit. Once beneficiaries are identified, it becomes easier to think about valuation, whether monetary or otherwise. Alternatively, perhaps the beneficiaries are other species besides humans, such as aquatic biota, but when we perform valuation we are talking about people, so in that case you’d want to tie the affected stream life (freshwater fish, for example) to its value to people. You’ll likely have to make some assumptions or decisions that are outside the scope of biophysical science and instead rely on social, political, cultural, or economic realities.
Once you’ve considered these ideas, researched the social structures of the region and people’s relationships with its natural resources, and examined who the beneficiaries may be, please feel free to respond here with any more specific questions. I hope this helps.