Natural-habitat shock (LUH2) — Habitats component

Source: LUH2 (Land-Use Harmonization 2, Univ. Maryland) Year: 2015 baseline → 2035 / 2050 / 2080 Category: Scenario · Habitats (Structural & Biotic Integrity) Coverage: Global Format: Raster grid (~0.25°) Used in risk analysis: Yes — drives the Habitats component of the Nature Stress Test (default NST_HABITATS_PROXY = luh2); not used in present-day materiality scoring.

What it shows

This layer family projects how the structural and biotic integrity of habitats at a site is expected to change under climate-and-land-use scenarios, relative to a 2015 baseline. It is the default data source for the Habitats ecosystem component (also called Structural & Biotic Integrity) in the Nature Stress Test, replacing the legacy EII Ecoregion shock proxy.

The underlying signal is the percentage of natural habitat remaining per cell, from the LUH2 land-use reconstruction and projections; the shock translates the change in that extent into a change in ecosystem integrity.

How it is built

Per cell, % natural habitat = (primf + primn + secdf + secdn) × 100 — the four natural land-state fractions in LUH2 (primary and secondary, forested and non-forested). The 2015 historical reconstruction gives the baseline; each scenario–horizon projection gives the future extent.

The extent is converted to ecosystem integrity through a Hill function that encodes the Andrén (1994) / Fahrig (2002) extinction thresholds — the well-established non-linear relationship in which integrity drops sharply once habitat extent falls below roughly 30 % (inflection) and cascades below ≈ 10 %. The shock is the change in that integrity between the 2015 baseline and the horizon, in percentage points (−100 … +100), with negative = integrity loss (the same sign convention as the EII Ecoregion and MSA shocks).

Two scenarios are produced from different integrated-assessment models — SSP1-2.6 (ssp126, RCP2.6, optimistic; IMAGE IAM) and SSP3-7.0 (ssp370, RCP7.0, high-end reference; AIM IAM) — each at three horizons. Native resolution is 0.25° global (EPSG:4326).

(The optional ssp245 and ssp585 pathways exist in the pipeline but are off by default.)

How to read it

Values are the projected change in habitat integrity in percentage points versus 2015. More negative = greater projected loss of structural & biotic integrity at that location; values near zero indicate stability; positive values indicate projected recovery of natural habitat. Read the scenario and horizon in the layer name together — e.g. ssp370-2080 is the high-end pathway at the most distant horizon.

Class thresholds

The underlying quantity is a change-of-condition flux: the projected change in Andrén/Fahrig ecosystem integrity (a Hill function of % natural habitat), in percentage points vs the 2015 baseline. The layer is rendered as a continuous symlog diverging gradient rather than discrete risk classes:

The companion baseline layer (luh2-natural-habitat-historical-2015) is a linear 0–100 % extent surface (red → green), not a shock.

How these thresholds were set. The shock quantity comes from the LUH2 extent passed through the Andrén 1994 / Fahrig 2002 extinction-threshold Hill function — a published ecological relationship, not a Darwin-invented break. The Habitats component's threshold logic (the 30 % / 10 % extent inflection points) is applied in the Nature Stress Test engine; the layer itself carries no per-pixel proximity flag, and the −100 / 0 / +100 pp gradient endpoints are a symmetric in-house display choice.

Source

Land-Use Harmonization 2 (LUH2 v2), University of Maryland — Hurtt et al. (2020), Geoscientific Model Development. Extinction-threshold method: Andrén (1994); Fahrig (2002). Open data; native 0.25°, annual.

Comparison with the WWF Risk Filter Suite

This is a forward-looking, horizon-resolved scenario layer and has no direct equivalent in the WWF Risk Filter Suite, which publishes present-day indicators only. It should be treated as a Darwin extension that projects ecosystem-integrity trajectories WWF does not itself produce. It supersedes the single-horizon EII Ecoregion-shock proxy for the Habitats component.

Legend

Symbolised field: Natural habitat shock (pp)

Generated from darwin/layers/layer-luh2-shock-*.toml and layer-luh2-natural-habitat-historical-2015.toml (develop).