The inventory at a glance

Malmö’s municipal tree inventory records 83,596 individual trees across 391 taxa. Using global occurrence data from GBIF we were able to build climate profiles for 308 species, covering 73% of all trees in the city. The remaining trees are either identified only to genus level or belong to rare taxa without enough occurrence data to estimate a reliable climate envelope.

Native vs exotic composition of the Malmö inventory.

The inventory is almost evenly split between Nordic-native and exotic species. Around 3,997 trees have no origin recorded.

Top species by origin and climate suitability

The chart below shows the 25 most common species, coloured by their climate suitability under the 2090 SSP5-8.5 scenario. Green bars mark species whose global climate niche already encompasses conditions similar to those projected for Malmö by the end of the century. Red bars highlight species whose climatic comfort zone is far from where Malmö is heading — these are the ones most likely to struggle as temperatures rise and moisture balance shifts.

Top 25 species coloured by projected climate suitability, faceted by origin.

Top 25 species coloured by projected climate suitability, faceted by origin.

How we measure “suitability”

For each species we collected global occurrence records from GBIF and extracted the temperature and moisture conditions at each location using WorldClim climate data at ~1 km resolution. The median temperature and moisture index across all those occurrences defines the species’ climate centre. We then measure how far that centre is from the projected conditions in Malmö under the worst-case 2090 scenario (SSP5-8.5: +4.5 °C warming, drier summers). Species whose climate centre is close to the 2090 projection are labelled well-suited; those far away are labelled high risk.

Crown diameter distribution

Crown diameter distribution. The 2,181 trees with no recorded measurement (diameter = 0) are excluded.

Planting history

Number of trees planted per year (valid records 1900–2025). The 1,833 trees recorded with planting year 0 are excluded.

Planting context

Trees by planting context (standort). Unknown category excluded.

Climate space: where Malmö’s trees sit today

The plot below places every species in Malmö’s inventory into a two-dimensional climate space defined by mean annual temperature (x-axis) and climatic moisture index (y-axis). The density contours show where most species cluster. The dashed arrow traces Malmö’s projected climate shift from current conditions through to 2090 under the high-emissions scenario.

Seven indicator species are labelled to illustrate the range of climate positions present in the inventory.

Climate space of Malmö's urban forest (wild-branch GBIF occurrences, 307 species). Dashed arrow = Malmö warming trajectory.

Climate space of Malmö’s urban forest (wild-branch GBIF occurrences, 307 species). Dashed arrow = Malmö warming trajectory.

What the climate space tells us

Most of Malmö’s tree species cluster around 8–12 °C mean annual temperature and slightly positive moisture — broadly consistent with the maritime climate of northern Europe. But the 2090 high-emissions trajectory pushes Malmö into territory around 13 °C and slightly negative moisture, which is beyond the core climate envelope of the majority of species currently planted.

A few key observations from the seven indicator species:

  • Betula pendula (silver birch, 1,838 trees): already sits at the warm edge of its climate range at Malmö’s current temperature.

  • Fagus sylvatica (European beech, 4,811 trees) and Tilia × europaea (common lime, 4,942 trees): the two most abundant species. Both are currently well placed but the 2090 projection sits beyond their 95th percentile for temperature.

  • Gleditsia triacanthos and Platanus × hispanica: warmer-climate species already present in the city whose climate centres are close to the 2090 projection.

  • Fraxinus angustifolia: a warm/dry-adapted species whose climate niche extends beyond even the 2090 scenario — a candidate for future expansion planting.

Where is climate risk concentrated?

How the risk score is calculated

Each species is assigned a climate risk score — a single number summarising how far its current climate niche is from where Malmö’s climate is projected to be by 2090.

Step 1 — Climate centre. For each species we use global wild-occurrence records from GBIF paired with WorldClim bioclimatic rasters (~1 km). The median value across all occurrence-linked raster cells gives the species’ climate centre: one value for mean annual temperature (bio1, °C) and one for the climatic moisture index (CMI, dimensionless).

Step 2 — Standardise. Because temperature and moisture are on different scales, each variable is divided by its standard deviation across all species in the dataset (bio1 SD = 2.55 °C; CMI SD = 0.20).

Step 3 — Euclidean distance. The risk score is the straight-line distance in this standardised two-dimensional space between the species’ climate centre and the projected 2090 SSP5-8.5 conditions for Malmö (+4.5 °C, bio1 = 13.0 °C; CMI ≈ −0.02):

\[d = \sqrt{\left(\frac{\tilde{T}_{sp} - T_{2090}}{\sigma_{T}}\right)^{2} + \left(\frac{\widetilde{CMI}_{sp} - CMI_{2090}}{\sigma_{CMI}}\right)^{2}}\]

Thresholds. \(d < 1\) = well-suited to 2090 (2090 Malmö climate lies within roughly one standard deviation of the species’ centre); \(1 \leq d < 2\) = moderate risk; \(d \geq 2\) = high risk.

The map below shows a smoothed surface of climate risk across the city. Each tree is assigned its species’ climate distance from the 2090 SSP5-8.5 scenario. The surface is averaged over a ~200 m grid and smoothed to reveal neighbourhood-level patterns. Red areas contain trees whose species are, on average, furthest from future conditions. Green areas are dominated by species already suited to a warmer, drier Malmö.

Neighbourhood-level climate risk. Red = high average mismatch with 2090 conditions.

Reading the map

A high risk score does not mean a tree will die — it means the species’ global climate profile is far from where Malmö’s climate is heading. Use this as a screening tool: red neighbourhoods may warrant closer monitoring or diversified replanting as individual trees reach the end of their productive life.

Risk summary by species

Top 30 species by abundance with climate risk classification.
Species Trees Origin 2090 suitability Risk score Median temp (°C) Median CMI
Tilia × europaea 4,942 Exotiskt Moderate risk 1.4 9.5 0.04
Fagus sylvatica 4,811 Nordiskt Moderate risk 1.7 9.1 0.10
Prunus avium 3,221 Nordiskt Moderate risk 1.3 9.7 0.02
Quercus robur 2,785 Nordiskt Moderate risk 1.5 9.3 0.05
Acer campestre 2,714 Nordiskt Moderate risk 1.2 9.9 -0.03
Acer platanoides 2,104 Nordiskt High risk 2.2 7.5 0.05
Carpinus betulus 2,048 Nordiskt Moderate risk 1.2 9.9 -0.03
Aesculus hippocastanum 1,952 Exotiskt Moderate risk 1.4 9.6 0.05
Betula pendula 1,838 Nordiskt High risk 2.0 8.0 0.09
Acer pseudoplatanus 1,826 Exotiskt Moderate risk 1.6 9.2 0.12
Platanus × hispanica 1,768 Exotiskt Well-suited to 2090 0.4 12.2 -0.05
Fraxinus excelsior 1,716 Nordiskt Moderate risk 1.6 9.2 0.08
Pinus nigra 1,607 Exotiskt Moderate risk 1.3 9.7 0.00
Crataegus monogyna 1,128 Nordiskt Moderate risk 1.3 9.8 0.03
Tilia cordata 1,080 Nordiskt High risk 2.3 7.2 0.03
Populus nigra 1,045 Exotiskt Moderate risk 1.1 10.6 -0.12
Gleditsia triacanthos 875 Exotiskt Well-suited to 2090 0.7 11.8 -0.12
Robinia pseudoacacia 861 Exotiskt Moderate risk 1.1 10.3 -0.07
Sorbus aucuparia 846 Nordiskt High risk 2.5 7.2 0.16
Metasequoia glyptostroboides 810 Exotiskt Moderate risk 1.1 11.8 0.18
Alnus glutinosa 787 Nordiskt Moderate risk 1.8 8.8 0.09
Thuja plicata 782 Exotiskt High risk 2.0 9.5 0.28
Prunus sargentii 711 Exotiskt Moderate risk 1.9 10.3 0.29
Crataegus × lavalleei 681 Exotiskt Moderate risk 1.6 9.0 -0.04
Populus simonii 628 Exotiskt Moderate risk 1.9 8.2 -0.08
Quercus rubra 574 Exotiskt Moderate risk 1.5 9.5 0.09
Malus domestica 567 Exotiskt Moderate risk 1.9 8.1 0.04
Acer saccharinum 549 Exotiskt Moderate risk 1.2 10.0 -0.02
Salix × pendulina 526 Exotiskt Moderate risk 1.8 8.5 0.06
Prunus cerasifera 471 Nordiskt Moderate risk 1.2 9.9 -0.02

Interactive data table

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Key takeaways

  1. Most of Malmö’s dominant tree species face moderate to high climate risk by 2090 under the high-emissions scenario. The city’s two most common species — Tilia × europaea and Fagus sylvatica — have climate centres that the 2090 projection exceeds.

  2. The exotic fraction already contains well-suited future species. Gleditsia triacanthos, Platanus × hispanica, and Fraxinus angustifolia are all present in the inventory and well positioned for warmer, drier conditions.

  3. Risk is not evenly distributed across the city. The map above shows that some neighbourhoods carry a heavier concentration of climate-vulnerable species; these should be prioritised for diversification as part of routine replanting.

  4. Native does not equal safe. Several Nordic-native species (Betula pendula, Sorbus aucuparia) are near or beyond their warm-edge limits at current temperatures.

  5. Data quality matters. Hybrid taxa such as Tilia × europaea and Platanus × hispanica appear as wild observations in GBIF even though they are almost exclusively planted trees — their envelopes reflect where they have been planted, not where they grow naturally.

Data sources: Malmö municipal tree inventory (2023), GBIF occurrence records (Jan 2026, DWCA download), WorldClim bioclimatic variables (30 arc-sec, 1970–2000 baseline), SMHI climate projections for Skåne.