SEDI Index Split, Croatia 2025: What the First SEDI Assessment Tells Us About Seasonal Ecological Debt

Tourism destinations are often described through annual numbers.

Annual arrivals. Annual overnight stays. Annual water consumption. Annual energy demand.

But destinations do not experience tourism evenly throughout the year.

For many places, particularly across the Mediterranean, tourism arrives in waves.

During peak periods, the number of people using local roads, water systems, energy infrastructure, public spaces and waste services can increase significantly. Months later, much of that additional demand disappears.

Annual averages can therefore tell us something important while still hiding another part of the story:

This question became the starting point for the Seasonal Ecological Debt Index (SEDI) developed by Green Path Alliance.

In 2026, we completed the first pilot application of the methodology.

The destination was Split, Croatia.

And the result gave us much more than a single number.

The Split SEDI Result

The pilot assessment produced an overall:

But SEDI deliberately does not stop there.

Alongside the final score, the Split assessment reports:

These additional values are fundamental to understanding the assessment.

A score tells us the result.

Data Coverage tells us how much of the assessment could actually be supported by available evidence.

Assessment Confidence tells us how strongly the available evidence supports the conclusions being presented.

This means that when readers see 51.80, they do not have to accept an unexplained sustainability rating. They can also ask:

• How much data was available?
• How reliable was that evidence?
• Which pressures produced the result?
• And where did the information come from?

That is exactly how SEDI is intended to be read.

How to Read a SEDI Score

A higher SEDI score represents greater seasonal ecological pressure.

It does not automatically mean that a destination is unsustainable.

Likewise, a lower score does not mean that sustainability management is complete.

SEDI is designed to identify pressure, not assign blame.

For that reason, a SEDI result should always be considered together with four elements:

For Split, this means:

• 51.80 / 100 — Moderate Ecological Debt
• 94.44% — Data Coverage
• 90.82% — Assessment Confidence / Very High

The objective is simple:

Six Dimensions Tell the Real Story

The overall SEDI score is calculated from six interconnected dimensions representing different forms of seasonal destination pressure.

The Split pilot produced the following profile:

This is where the assessment becomes considerably more useful than the headline score.

Split does not experience the same level of pressure everywhere.

Some systems are carrying significantly greater seasonal demand than others.

Tourism & Mobility: Split's Strongest Pressure

With a score of 70/100, Tourism & Mobility represents the strongest pressure identified in the pilot assessment.

This reflects the interaction between visitor intensity, peak-season concentration and mobility demand within a city that serves several functions simultaneously.

Split is not simply a tourism destination.

It is a residential city, an administrative and economic centre, a major transport hub and an important gateway to the Croatian islands and wider Adriatic region.

During peak tourism periods, these functions overlap.

More visitors mean more movement, more demand on transport systems and greater concentration within already highly used urban areas.

SEDI therefore identifies mobility as an area where targeted improvements could have a particularly meaningful effect on future seasonal ecological debt.

The objective is not to reduce mobility.

It is to make seasonal mobility more efficient, accessible and increasingly low-emission.

Energy, Emissions & Air: Seasonal Demand Matters

The Energy, Emissions & Air dimension scored 56/100.

Tourism-related energy consumption does not occur independently from the needs of the resident population.

Accommodation, hospitality, transport and other visitor services increase electricity demand during periods when Mediterranean temperatures can simultaneously increase cooling requirements across homes and businesses.

That interaction matters.

A destination may have sufficient annual energy capacity while still experiencing meaningful seasonal pressure.

For Split, the assessment therefore highlights opportunities around energy efficiency, renewable-energy adoption, cleaner mobility and stronger monitoring of seasonal energy demand.

Socio-cultural Load: Sustainability Includes Residents

Split recorded 53/100 for Socio-cultural Load.

This dimension is important because ecological debt is not only about electricity, water or emissions.

Tourism happens inside communities.

Seasonal concentration can affect public-space use, mobility, congestion, housing conditions, employment patterns and the relationship between residential and visitor activity.

This becomes particularly important in historic cities where the places attracting visitors are also places where people live, work and move through their everyday lives.

SEDI therefore treats the resident experience as part of destination sustainability rather than as a separate tourism issue.

Waste & Water: Capacity With Pressure to Monitor

Waste & Water Pressure recorded 50/100.

Tourism increases temporary demand for freshwater, wastewater treatment and municipal waste services.

At the same time, Mediterranean destinations increasingly have to consider water availability, heat and changing climatic conditions.

The Split assessment identified wastewater infrastructure as an important area of resilience while recognising that seasonal resource demand still requires monitoring and long-term planning.

This distinction is important.

Land, Ecosystems & Biodiversity: An Area of Relative Resilience

At 36/100, Land, Ecosystems & Biodiversity represents one of the lower-pressure dimensions within the Split assessment.

This suggests that ecological conditions and protected natural areas currently provide an important element of resilience within the destination profile.

But a relatively low pressure score should never become an excuse to stop monitoring.

Coastal ecosystems, natural landscapes and biodiversity are part of the environmental foundation on which tourism itself depends.

Urban development, increasing visitation and climate change can alter these conditions gradually.

Governance & Data Transparency: Split's Strongest Relative Performance

The lowest pressure score in the assessment was recorded within Governance & Data Transparency: 25/100.

And this deserves particular attention.

Good environmental management requires more than good intentions.

Destinations need information.

They need public statistics.

They need plans.

They need transparent institutions.

And they need enough evidence to understand whether interventions are actually producing results.

For the Split pilot, the availability of Croatian and European public data was essential.

Green Path Alliance would therefore like to acknowledge the contribution of the Croatian public institutions, governing bodies and tourism organisations whose publicly accessible information made a transparent assessment possible.

Good sustainability methodologies depend on good evidence.

And good evidence depends on institutions willing to make information accessible.

94.44% Data Coverage: Why This Number Matters

We are particularly proud of the 94.44% Data Coverage achieved during the Split pilot.

Not because 100% should always be expected.

Quite the opposite.

One of the principles behind SEDI is that sustainability assessments should be transparent about what they do not know.

Missing data should not disappear behind a final score.

Where destination-level information is unavailable, SEDI can use a transparently documented proxy where an appropriate methodological relationship exists.

Where evidence remains unavailable, that limitation should be visible.

This is why Data Coverage accompanies the SEDI result.

90.82% Assessment Confidence: Showing the Strength of the Evidence

The Split assessment achieved 90.82% Assessment Confidence — Very High.

Assessment Confidence considers the quality, relevance, transparency and completeness of the evidence supporting the assessment.

Official statistics, recognised international datasets and transparent methodologies therefore contribute differently to confidence than weaker or less geographically precise evidence.

Again, the purpose is not to claim certainty.

It is to communicate uncertainty honestly.

There is an important difference.

What Is Creating Split's Seasonal Ecological Debt?

Looking across all six dimensions, the Split pilot identified several principal pressure areas.

The strongest is Tourism & Mobility, followed by pressures associated with seasonal energy demand, visitor concentration and socio-cultural load.

At the same time, the assessment identifies meaningful areas of resilience, particularly within Governance & Data Transparency and Land, Ecosystems & Biodiversity.

This creates an important conclusion.

Split does not need to improve every sustainability dimension equally.

Instead, the assessment provides a basis for prioritisation.

From Measurement to Improvement

SEDI is not designed to end with a score.

The score establishes a baseline.

For Split, the assessment points toward several directions for continued improvement.

The objective is not to eliminate tourism pressure completely.

The objective is to ensure that seasonal demand remains within the destination's capacity to respond sustainably.

Why Split Was an Important First Pilot

The purpose of the Split assessment was never to demonstrate that a destination was either sustainable or unsustainable.

It was to test whether seasonal ecological pressure could be assessed in a way that was:

Split provided an excellent environment for that first application because it combines significant tourism intensity with permanent urban life, complex mobility patterns, environmental resources and relatively strong public-data availability.

The result is now established as:

But GP-001 should not be understood as the final word on Split.

It is a baseline.

As new evidence becomes available and future assessments are completed, the methodology can show whether seasonal ecological debt is increasing, remaining stable or being reduced.

An Open Methodology Must Be Open to Improvement

SEDI will continue developing.

Future applications across municipalities, countries and larger geographic areas will test the methodology under different tourism patterns, environmental conditions and levels of data availability.

Where stronger evidence becomes available, it should replace weaker evidence.

Where an indicator can be improved, the methodological reasoning should be documented.

Where limitations exist, they should be communicated.

The purpose is not to create an index that can never be questioned.

It is to create one that can be understood, tested and improved.

Because sustainability itself is not a finished state.

Explore the Split SEDI Assessment

Readers interested in the complete assessment can explore GP-001 — SEDI Destination Assessment Report: Split, Croatia, which presents the six assessment dimensions, pressure drivers, improvement roadmap, methodology overview, Data Coverage, Assessment Confidence and evidence sources.

The Split assessment is the first entry in what will become a growing SEDI assessment library.

And although several assessments are already in development, we would also like to hear from our readers:

The first assessment started in Split.

The next chapter of the SEDI Index is already being written.