Lake Kournas: How Scientists Read 10,000 Years of Cretan Olive History in Mud

There is a lake in western Crete, nestled in a depression between the White Mountains and the sea, that holds no particular claim to grandeur. Lake Kournas is small — you could walk its circumference in under an hour — and its waters, though clear enough to reveal the terrapins drifting beneath the surface, do not inspire the reverence of deeper, older bodies of water elsewhere in the Mediterranean. It is, however, the only natural freshwater lake on the island, and this singularity has made it quietly indispensable to science. For beneath its bed, compressed into fine laminations of clay, silt, and organic matter, lies a continuous environmental archive stretching back ten thousand years. It is a record written not in stone tablets or palace frescoes, but in pollen grains, charcoal fragments, and the chemical signatures of a landscape in constant, slow negotiation with the people who have worked it.

In 2021, a team of researchers published their findings in Quaternary Science Reviews after extracting a 15-metre sediment core from beneath Lake Kournas. The core, drilled through successive layers of lakebed material, captured an unbroken environmental narrative spanning the entire Holocene — from the centuries before the first deliberate cultivation of olives on Crete to the mechanised agriculture of the present day. What it revealed was not a simple story of progress, of steady agricultural advance from primitive beginnings to modern efficiency. Instead, the record described something far more interesting: a pattern of cultivation, abandonment, recovery, and renewed cultivation, repeating across millennia in waves that correspond closely to the rise and fall of the civilisations that have called Crete home.

Reading the Mud

Sediment cores are, in essence, columns of compressed time. Each layer represents a period during which material — wind-blown dust, eroded soil, pollen from surrounding vegetation, microscopic charcoal from fires both natural and human-set — settled to the bottom of the lake and was gradually buried by the material that followed. The deeper you drill, the further back you travel. A trained palynologist, examining these layers under a microscope, can identify the pollen of specific plant species and track their abundance over centuries. When olive pollen increases in a given stratum, it signals the expansion of olive groves in the surrounding landscape. When it declines, replaced by the pollen of wild scrubland species — mastic, cistus, wild grasses — it tells of groves abandoned, of terraces left to weather and erode, of a landscape reverting to its own devices.

The Kournas core revealed three distinct waves of olive cultivation across its ten-thousand-year span. The first corresponds to the Final Neolithic and the subsequent Minoan period, when the great palace civilisations of Knossos, Phaistos, and Malia transformed Crete into the commercial heart of the eastern Mediterranean. Olive oil was central to Minoan economy and ritual alike — stored in massive pithoi, traded across the Aegean, used to anoint the living and honour the dead. The pollen record shows a marked expansion of Olea europaea during this era, accompanied by increases in charcoal that suggest deliberate land clearance by fire to make way for groves.

Then came collapse. The reasons for the decline of Minoan civilisation remain debated — volcanic eruption, earthquake, invasion, internal upheaval — but the sediment does not equivocate about its ecological consequences. Olive pollen diminishes. The signatures of wild vegetation return. The landscape, released from the pressures of organised agriculture, begins a slow process of recovery, its biodiversity shifting back towards higher diversity as scrubland, maquis, and eventually woodland reclaim the terraced hillsides.

The Rhythm of Abandonment and Return

This pattern — expansion, collapse, ecological recovery — repeated itself. The second great wave of olive cultivation visible in the Kournas core corresponds to the Hellenistic, Roman, and Byzantine periods, an arc of nearly fifteen hundred years during which Crete passed through successive imperial hands, each of which recognised the economic value of its olive groves. Roman Crete was a significant oil producer, its output feeding the appetites of an empire that consumed olive oil not merely as food but as fuel for lamps, as a base for cosmetics and medicines, and as a lubricant for the machinery of daily life. The pollen record swells again with Olea, and the charcoal layers thicken once more.

And once more, decline followed. The fragmentation of Byzantine authority, the Arab conquest of the ninth century, and the subsequent centuries of contested control brought periods of agricultural contraction. Groves were neglected. Terraces crumbled. The landscape's natural resilience — that stubborn capacity for self-repair that characterises Mediterranean ecosystems — reasserted itself, and biodiversity recovered in the intervals between human ambition.

What is remarkable about these cycles is not the fact of human impact itself, which is hardly surprising, but the landscape's demonstrated capacity to absorb and recover from it. For thousands of years, the relationship between Cretan agriculture and Cretan ecology operated within boundaries that, however strained during periods of intensive cultivation, permitted recovery when pressure was removed. The olive groves of antiquity were not benign — they replaced native vegetation, altered soil chemistry, and redirected water flows — but they existed within a broader ecological context that retained enough resilience to bounce back. The sediment core, read carefully, describes not a pristine wilderness progressively degraded, but a dynamic system capable of oscillation, of give and take, of absorbing human activity and reasserting ecological complexity in its absence.

The Third Wave and Its Difference

The third wave of olive cultivation recorded in the Kournas core is the one we inhabit now, and it differs from its predecessors in ways that the sediment makes disturbingly clear. Beginning with the Venetian period and accelerating dramatically in the twentieth century, the modern expansion of olive cultivation on Crete has been characterised not merely by scale but by a fundamental change in method. The upper layers of the core — the most recent centuries, compressed into the topmost portion of the column — show a pattern unlike anything in the preceding millennia. Olive pollen dominates to an unprecedented degree. The signatures of wild vegetation are suppressed to levels not seen at any previous point in the ten-thousand-year record. And the indicators of biodiversity — the variety of pollen types, the presence of species associated with healthy, complex ecosystems — decline sharply.

In the last hundred years, the record suggests, biodiversity has markedly declined, probably in response to the industrialisation of agriculture. This is not the cyclical contraction visible in earlier periods, where wild species retreated but persisted in refugia — marginal areas, rocky outcrops, the edges of terraces — ready to recolonise when cultivation receded. The modern decline appears qualitatively different: deeper, more thoroughgoing, and — most troublingly — without the compensating intervals of recovery that characterised earlier millennia.

What the Groves Once Sheltered

To understand what is being lost, it helps to understand what traditional olive groves once sustained. A centennial olive grove managed in the old way — without herbicides, without mechanical weed clearance, with pruning by hand and harvest by hand or by beating the branches with long poles — is not a monoculture in any meaningful sense. It is, rather, a semi-natural habitat, a managed ecosystem in which the olive trees form a canopy over a rich and varied understorey of ground flora.

Research conducted by Cambridge University, which monitored the ground flora of olive groves subject to different management practices on Crete, found that traditional low-input groves supported far higher biodiversity than their intensively managed counterparts. The difference was not marginal. Traditional groves harboured diverse communities of ground-dwelling plants, including populations of rare orchid species — terrestrial orchids of the genera Ophrys and Orchis, whose complex relationships with pollinating insects make them particularly sensitive indicators of ecosystem health. These groves also supported diverse bird and insect populations, their gnarled, centuries-old trunks providing nesting cavities and shelter, their unpruned understorey offering food and habitat.

The physical setting of these groves contributes to their ecological character. Olive trees on Crete grow mostly on inclined, shallow, low-fertility soils, often on hand-made stone terraces constructed over centuries by successive generations of farmers. These terraces, built without mortar from locally gathered limestone, are themselves habitats — their crevices shelter lizards, insects, and drought-tolerant plants. The olive tree's famously modest watering requirements make it suited to these marginal landscapes where other crops would fail, and the traditional practice of allowing ground cover to grow beneath the trees helps to stabilise the thin soils and prevent erosion on the steep hillsides.

This is not a romantic idealisation. Traditional olive farming on Crete was hard, often poorly remunerated work, and the groves it produced were not wilderness preserves but working agricultural landscapes shaped by human need. But they were landscapes in which agriculture and biodiversity coexisted in a relationship that, however imperfect, had proven sustainable across millennia. The sediment core from Lake Kournas confirms as much: during the earlier waves of olive cultivation, the pollen record shows reduced but persistent biodiversity, a landscape altered but not stripped.

The Chemistry of Modern Decline

What changed in the twentieth century was not the olive tree itself but the systems imposed upon it. The introduction of synthetic herbicides, the mechanical clearance of ground vegetation, the application of chemical fertilisers to soils that had been managed for centuries without them — these interventions, adopted in the name of efficiency and yield, have transformed the ecology of Cretan olive groves in ways that have no precedent in the ten-thousand-year record.

Herbicide application eliminates the ground flora that sustains insect populations, which in turn sustain birds. Mechanical clearance of vegetation between and beneath trees strips the soil of the organic matter that protects it from erosion. The result, visible in groves across Crete and documented by researchers, is a progressive simplification of the ecosystem — a reduction in the number of species present, in the complexity of their interactions, and in the resilience of the system as a whole. Where a traditional grove might support dozens of plant species beneath its canopy, an intensively managed grove may support a handful, or none at all beyond the olive trees themselves, standing in bare, herbicide-treated earth.

The consequences extend beyond the boundaries of the groves. Eroded soil washes into watercourses and eventually into the sea. Reduced insect populations affect pollination of wild plants in adjacent areas. The loss of bird species ripples through food webs in ways that are difficult to predict and harder to reverse. The Cambridge research documented these effects with careful, systematic observation, and the Kournas sediment core provides the deep-time context that makes their significance clear: what is happening now is not a fluctuation within the normal range of a dynamic system, but a departure from the patterns that have governed this landscape for ten thousand years.

The Case for Tradition

There is, however, evidence that the trajectory is not inevitable. Studies of organic farming practices on Crete have found that organic operations achieve the highest eco-efficiency scores — a measure that accounts for both economic output and environmental impact — followed by other ecological approaches that limit chemical inputs and preserve traditional management practices. This is not merely an environmental argument; it is an economic one. Farms that work with the landscape rather than against it, that treat the grove as an ecosystem rather than a factory floor, produce oil of high quality while maintaining the ecological infrastructure on which long-term productivity depends.

The logic is not complicated, even if its implementation requires patience and a willingness to accept lower short-term yields. An olive tree on Crete can live for centuries — some specimens on the island are credibly dated to over a thousand years old. A farming system oriented around such trees must, by necessity, take a long view. The stone terraces on which they grow were not built in a season; they represent generations of accumulated labour and knowledge. The biodiversity they support is not a decorative amenity but a functional component of a system that has sustained food production on marginal soils for millennia. To strip it away in pursuit of a few decades of intensified output is to trade a renewable resource for a depleting one.

The sediment beneath Lake Kournas offers a perspective that no single human lifetime can provide. It shows that olive cultivation on Crete has been interrupted before — by war, by political collapse, by the ordinary entropy of civilisations — and that each time, the landscape recovered. It shows, equally, that the current mode of cultivation is producing ecological effects without precedent in the record. The question posed by the core is not whether Crete can grow olives — it has done so, with interruptions, for ten thousand years — but whether the way it grows them now is compatible with the ecological systems that have made such cultivation possible.

Mud, Memory, and What Endures

There is something humbling about the thought that a column of mud, extracted from the bed of a modest lake in western Crete, can contain more environmental history than all the written records of the island combined. The Minoans left Linear A and Linear B tablets, palace archives cataloguing oil and grain. The Romans left inscriptions and administrative records. The Venetians left census data and trade ledgers. But none of these sources can tell us what the Kournas core tells us: what grew on the hillsides, in what abundance, and how the living fabric of the landscape responded to the pressures placed upon it across a hundred centuries.

The core's testimony is not sentimental. It does not argue for a return to some imagined pastoral innocence, nor does it condemn agriculture as inherently destructive. What it demonstrates, with the quiet authority of physical evidence, is that there are modes of olive cultivation that the Cretan landscape can absorb and recover from, and there are modes that push it beyond its capacity for self-repair. For most of recorded and unrecorded history, Cretan farmers operated within the former category — not out of environmental consciousness in any modern sense, but because the tools and methods available to them imposed natural limits on the degree to which they could simplify the ecosystems they managed.

The removal of those limits, in the space of a single century, has produced results that the sediment record identifies as anomalous. Whether they prove irreversible depends on choices being made now, in this generation, by the people who tend the groves and by those who buy what they produce.

It is against this backdrop that the work of small Cretan producers takes on a significance beyond the commercial. Farms that maintain traditional groves, that harvest Koroneiki olives from ancient trees on stone-terraced hillsides without recourse to herbicides or intensive mechanical intervention, are not merely producing olive oil. They are sustaining a mode of cultivation that the ten-thousand-year record shows to be compatible with the ecological health of the landscape. The oil they produce — and it is this Cretan Koroneiki oil that Eliato brings to the table — carries within it the flavour of a particular place, a particular climate, a particular set of relationships between tree, soil, and the life that inhabits both. It is a flavour shaped not by industrial optimisation but by the slow accumulation of centuries, by shallow soils and strong sun and the unforced rhythms of a landscape that has been producing olives since before history began to be written down.

The mud beneath Lake Kournas will go on accumulating, layer by patient layer, recording whatever comes next. What it records will depend, in part, on whether the groves that surround it are managed as ecosystems or as production lines — and on whether those of us who use their oil consider that distinction worth preserving.