InVEST: A free tool for understanding the benefits provided by ecosystems

Tool

ABOUT THIS ISSUE

It is very difficult to plan and implement an NbS without first having an understanding of the benefits that the NbS provides

SOLUTION

InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) is a free software for visualizing the benefits provided by natural and modified ecosystems

Understanding and quantifying nature’s benefits

Natural ecosystems provide various benefits that people may be unaware of or unsure how to quantify. For example, residents or policymakers in a low-lying city may not be aware that a nearby upland forest is helping to reduce flooding (by reducing rainfall runoff) and maintain adequate water quality (by reducing soil erosion and runoff of pollutants) and quantity (by allowing for adequate groundwater recharge). Even if the residents/policymakers are aware of these benefits of the upland forest, it’s unlikely that they can accurately quantify them. If these upland forest ecosystems are undervalued, they could be at risk of being converted to other types of land-use like urban or agricultural land, which could negatively affect biodiversity (due to habitat loss) and human well-being (for example, due to increased flooding or water quality degradation).

Figure 1. Examples of InVEST user interfaces, shown for the Urban Flood Risk Mitigation model and the Coastal Vulnerability model.

InVEST tool

InVEST is a free software that helps to visualize and quantify the various benefits provided by natural and modified ecosystems. InVEST can be downloaded from the Stanford University “Natural Capital Project” website. Several models are currently included in the InVEST software package, including many that are useful for the evaluation of NbS. Some of the commonly used InVEST models include:

  • Carbon
  • Coastal Blue Carbon
  • Coastal Vulnerability
  • Crop Pollination
  • Crop Production
  • Habitat Quality
  • Habitat Risk Assessment
  • Offshore Wind Energy
  • Recreation
  • Reservoir Hydropower Production (Water Yield)
  • Scenic Quality
  • Seasonal Water Yield
  • Sediment Retention
  • Urban Cooling
  • Urban Flood Risk Mitigation
  • Water Purification
  • Wave Energy

These models can be used to assess the benefits of ecosystems for addressing a range of environmental and social challenges, thus supporting the planning and implementation of NbS.

InVEST models for the example of water-related benefits of upland forests

With regards to the previously described challenge of quantifying the various benefits provided by upland forests to the residents of nearby low-lying cities, several InVEST models can be utilized. For example, the Urban Flood Risk Mitigation model, the Sediment Retention model, and the Water Purification model. The Urban Flood Risk Mitigation model is explained in more detail below.

Urban Flood Risk Mitigation model

The Urban Flood Risk Mitigation model can be used to quantify the stormwater runoff mitigation benefits provided by forests (and/or other types of land-use/land-cover), considering parameters like the amount of vegetation cover and the soil properties of the land. More specifically, a “Curve number” is calculated at each location in a study site (e.g., over a 30 meter x 30 meter grid map) taking into account the land-use/land-cover and soil characteristics (Soil Conservation Service 1986), as shown in Table 1. Lower Curve number values indicate less runoff, i.e., more rainfall retention by the land.

Table 1. Curve number of values of different combinations of land-use/land-cover and soil types. Higher Curve number values indicate higher stormwater runoff rates, meaning they contribute more to flooding of downstream areas.

Maps of Curve number values can be output from the InVEST model to show areas where runoff retention is very high (i.e., locations with low Curve number values). In many cases, these areas will contain forest lands, as forests have very low Curve number values due to their high levels of vegetation cover. This can be seen in Figure 2.

Figure 2. Maps of two sites in the Philippines showing land-use/land-cover (left) and corresponding Curve number (right). Lower Curve numbers on the map (shaded in green) indicate less stormwater runoff (i.e., more retention of the rainfall by the land), which can be mainly seen in areas having forest cover (also shaded in green).

The Curve number is not a direct indicator of the volume of runoff retained, as this will vary based on the intensity of a rainfall event. However, it is possible to calculate the volume of runoff retained at each location on the map based on the Curve number if the user inputs the amount of rainfall for a specific storm event. The rainfall amount to input for this model could be determined by referring to local meteorological records, e.g., by identifying rainfall amounts that have resulted in flooding in the past.

Tips for planners

Outputs of InVEST models are typically maps showing quantitative or qualitative information related to the benefits of ecosystems. These maps can be used as a basis for NbS planning in different ways. For example, the InVEST model(s) can be run before and after a potential NbS (new forest area) is added to the existing land-use/land-cover map to evaluate the benefits of the NbS.

Tips for technical staff

Common types of input data for InVEST models include land-use/land-cover maps, digital elevation models, and soil type maps. If no official datasets are available locally, it is possible to find free global or regional datasets from various sources, including Google Earth Engine and the USGS Data Explorer. The Asia-Pacific Climate Change Adaptation Information Platform, or “AP-PLAT”, website has a list of additional sources of data that may be useful inputs for InVEST. Free Geographic Information Systems software like QGIS can be used to prepare these input datasets for importing into InVEST.

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