Appendix G: Calculating Ecosystem Services with InVEST

1 Purpose of this appendix

Throughout this book, ecosystem services have appeared as:

  • productive assets,
  • risk buffers,
  • and pathways through which nature enters the economy.

This appendix shows how those services are actually calculated in practice using
InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs)—
the open-source modeling suite developed by the Natural Capital Project.

InVEST is one of the most widely used tools in the world for translating:

land cover → biophysical processes → ecosystem services → human outcomes

It is the ecological half of many Earth–economy systems.

2 What InVEST is (and is not)

InVEST is:

  • a modular suite of ecosystem service models,
  • spatially explicit,
  • process-based,
  • open-source,
  • designed for decision support.

It is not:

  • a single monolithic model,
  • a general equilibrium system,
  • or a forecasting oracle.

Each InVEST model answers a focused question such as:

  • How does land cover affect annual water yield?
  • How does habitat fragmentation affect pollination?
  • How do wetlands reduce flood risk?
  • How much carbon is stored in this landscape?

Earth–economy models use InVEST outputs as inputs.

3 The basic pattern

Every InVEST model follows the same conceptual pipeline:

  1. Inputs
    • Land-use / land-cover map
    • Biophysical parameter tables
    • Climate or hydrology data
    • Optional socio-economic layers
  2. Process
    • Apply ecological relationships
    • Move water, sediment, nutrients, carbon, or species
    • Aggregate effects across space
  3. Outputs
    • Raster maps of service supply
    • Tabular summaries by region or watershed
    • Optional valuation layers (where appropriate)

This is Earth–economy modeling at the landscape interface.

4 A concrete example: Water yield

The InVEST Water Yield model estimates:

How much water is produced by each pixel of land each year.

Inputs:

  • annual precipitation,
  • potential evapotranspiration,
  • land cover,
  • soil depth,
  • plant available water content.

Core idea (conceptual):

WaterYield = Precipitation − Evapotranspiration

But evapotranspiration depends on:

  • vegetation type,
  • rooting depth,
  • soil properties.

Thus a forested pixel and a cropland pixel receiving the same rainfall
produce very different water yields.

Outputs:

  • a raster of annual water yield,
  • watershed-level totals,
  • optional downstream flow accumulation.

Earth–economy use:

  • feed water availability into agriculture,
  • assess impacts of land-use change,
  • evaluate tradeoffs between forest and crop expansion.

5 Another example: Pollination

The InVEST Pollination model estimates:

  • habitat suitability for pollinators,
  • distance-weighted pollination supply,
  • crop yield enhancement.

Inputs:

  • land cover,
  • nesting suitability by land type,
  • floral resources,
  • crop locations,
  • foraging distances.

Core idea:

Crops closer to high-quality habitat receive more pollination.

Outputs:

  • maps of pollinator abundance,
  • maps of pollination-dependent yield,
  • farm-level production changes.

Earth–economy use:

  • link habitat loss to agricultural productivity,
  • evaluate restoration benefits,
  • internalize biodiversity into production systems.

6 Carbon storage and sequestration

The InVEST Carbon model:

  • assigns carbon pools to each land-cover type:
    • aboveground biomass,
    • belowground biomass,
    • soil,
    • dead matter.

For each pixel:

TotalCarbon = C_above + C_below + C_soil + C_dead

Land-use change between two maps:

Sequestration = Carbon_future − Carbon_current

Outputs:

  • carbon stock maps,
  • sequestration maps,
  • total change summaries.

Earth–economy use:

  • link land policy to emissions,
  • evaluate mitigation pathways,
  • embed carbon stocks in inclusive wealth.

7 Why this matters for Earth–economy models

InVEST provides:

  • spatially explicit,
  • biophysically grounded,
  • policy-sensitive

estimates of ecosystem services.

Earth–economy models provide:

  • price formation,
  • income effects,
  • trade responses,
  • intertemporal dynamics.

Together, they form:

A coupled system where land decisions alter services,
services alter productivity and risk,
and economic responses reshape land.

This is the core of Earth–economy modeling.

8 Strengths and limits

Strengths:

  • Transparent assumptions
  • Modular structure
  • Global applicability
  • Open-source
  • Decision-focused

Limits:

  • Not a general equilibrium model
  • Requires good spatial data
  • Simplifies ecological complexity
  • Does not model institutions or behavior

InVEST answers:

“What does this landscape provide?”

Earth–economy models answer:

“What happens when societies respond?”

Neither is sufficient alone.

9 Exercises

  1. Service mapping.
    Choose one ecosystem service (water, carbon, pollination, flood mitigation).
    List:
    • the land features that affect it,
    • the human activity that depends on it,
    • one policy that could change it.
  2. Pipeline thinking.
    Draw the chain:

Land-use policy → Land cover → InVEST output → Economic outcome

Fill in each step for a real example.

  1. Model design.
    Suppose you are building an Earth–economy model for a river basin.
    Which two InVEST services would you most want to include? Why?

InVEST is where the Earth meets the economy in pixels.

It turns:

  • forests into flood buffers,
  • habitat into yield,
  • wetlands into risk reduction,
  • and land into capital.

Earth–economy modeling is what happens next.