A peat bog without water acts like a compost pile. Prof. Viktor Kotovsky explains what degrades wetlands

In wetlands, the most important things happen where you can’t see the water table. A few, several centimeters below the surface will determine whether the bog acts as a storage and filter, or starts to work as a compost pile. Wet and cold winter can give a false sense of security – because snow and snowmelt look like abundance. What matters for wetlands, however, is not how much water has fallen, but how much is left in the catchment area. Prof. In an interview with Agnieszka Hobot, Wiktor Kotowski sorts out the key facts: desiccation is the main mechanism of wetland degradation, and restoration is not flooding, but the permanent restoration of the water regime. He also stresses that without coordinated action in agriculture, forestry and water management, wetlands cannot be effectively protected.

Agnieszka Hobot: When talking about wetlands, the words water, peat, process are often mentioned. If you had to name three key indicators that would scientifically determine whether a wetland is functioning properly, what would they be?

Wiktor Kotowski: First of all, wetlands are very different. This concept is so broad that in the broadest context it is worth using the definition that the Ramsar Convention adopts. Especially if we are talking about protection, because under this convention not only wetlands, including marshes, are protected, but also inland waters: lakes, rivers, floodplains and even coastal marine waters. And this immediately shows that it is impossible to choose a single criterion to evaluate all types of wetlands.

However, if I were to point out something in common, it would be that they should have as much water as the reference condition for the type predicts. And this immediately leads to the conclusion that the biggest problem and the main cause of degradation of all types of wetlands is desiccation. The second factor that comes to mind here is water pollution.

A.H.: We have had a wet and cold winter: lots of water, frost, and then thawing. Is such a winter from the point of view of wetlands and peatlands helpful or rather dangerous? What happens to the water in the peat and soil then, and how do you know if a wetland is going through this period well?

W.K.: Let me start by briefly clarifying an important point. Marshes account for roughly half of all wetlands worldwide. In their natural state, they are marshes. I use the term bog to describe areas with naturally accumulated peat, i.e. a drained bog remains one as long as there is a peat deposit.

On the other hand, in order for a peatland to be healthy and function as a carbon-accumulating system, it must have swampy conditions. What does it mean? The peat should be saturated with water more or less all year round. The water doesn’t have to be visible on the surface, it’s usually a few or a dozen centimeters below, but in general most of the peat should be wet year-round. The top layer may freeze during a cold winter, but there is water below anyway. First of all, because if we are talking about underground resources, water arrives there at a temperature well above zero – in our conditions it can be several, even up to 10°C. Secondly – there are processes in this layer that warm it a bit, because the heat is given off, among other things, by the anaerobic life that takes place there.

This year’s winter is different from many previous winters because of the cold weather, the considerable amount of snow, and the fact that this snow stays in the field precisely because of the negative temperature. This is important for bog systems, because snowmelt water can recharge them – if the snow stays within the bog and its catchment area, and then melts and soaks in.

Almost all of our peatlands have a catchment area, just like rivers. It should be remembered that in Poland more than 90 percent of them are low peatlands, originally fed by groundwater. And for groundwater to be effective in this regard, rainwater must soak into the ground in the catchment area of the peatland. The longer the snow lasts in the area, the greater the hope that it will feed the aquifers after the melt, which then flow into the bog areas and sustain their hydration.

The problem is that more than 85 percent of Poland’s peatlands, as well as areas in their catchment areas, are reclaimed, cut by ditches that drain this water before it can feed the system.

A.H.: We have a lot of drained peatlands in Poland. What happens to the peat then: what processes does the drainage set in motion and how does this affect water retention and quality?

W.K.: A peat bog is a specific ecosystem, which in a sense is never in equilibrium. A natural peat bog in a swampy state accumulates peat, that is, we have an imbalance in the carbon balance, in that this element keeps increasing in the system. This is because the existing peat deposit is saturated with water and therefore the organic matter it contains decomposes more slowly than new organic matter is supplied. So successive generations of plants add some biomass, the organic matter increases, and thanks to this, peat bogs accumulate more and more water, increase retention and, in a sense, purify groundwater, because some compounds, including nutrients, are trapped in them (this is an additional mechanism, besides microbiological processes, for the purification of water by peat bogs).

A drained peatland is also unsustainable in a sense, only much more so and in the opposite direction. Instead of a positive carbon balance, we have a negative balance as a result of its release in the form of_CO2. Peat that has accumulated in the swamp for millennia, when in contact with oxygen, decomposes at a rate several or even dozens of times faster than it accumulated. In principle, it can be compared to a large compost heap. Peat is the dead remains of plants that naturally lay in a kind of large barrel of water: there was more and more of it, growing by about 1 mm per year. And when we lower the water level – and it doesn’t have to be a very deep drainage, just a few tens of centimeters, according to the old intentions of land reclamationists – this layer of peat, exposed to oxygen, begins to behave like organic matter on a composter – it decomposes under the influence of fungal and bacterial activity.

And then the elements that were previously bound in the peat are released very quickly: nitrogen and phosphorus, previously contained in organic compounds, are oxidized to nitrates and phosphates. The water, instead of being depleted of biogenes, begins to be enriched in them. The process of converting peatland into peat-muck soils is set in motion, and the carbon that was once taken up by plants as_CO2 and stored underground for millennia is now being returned to the atmosphere at a rate many times faster.

At the same time, as the water level drops under drainage, the peat bog settles. We are talking about the disappearance of peat at a rate of millimeters to even a few centimeters per year. In the beginning, the process happens faster, because compaction of the peat due to water loss is still taking place. Later, the process of subsidence due to decomposition dominates. Its effect is the loss of about 1.5 centimeters of peat per year, that is, subsidence takes place about fifteen times faster than the growth.

Some of the substances contained in the peat, especially nitrogen in bioavailable forms, pass into shallow groundwater, into ditches and further into receiving bodies. Peatlands, which previously improved water quality, begin to pollute it. Added to this is the huge release of carbon dioxide: 1 hectare of drained peatland can generate annual emissions comparable to a passenger car traveling several hundred thousand kilometers. These are some of the largest land-use emissions per unit area that we see at all.

Nature in such areas is also changing – and drastically. Species adapted to bog conditions, which have no chance to occur anywhere else, are displaced by common, fast-growing plants. If the bog was transformed into a meadow, and this was most often the case, grasses enter. If the drained peatland is not used, it is occupied by shrubs and scrubs. As a result, typical peatland species have become very rare. Today we try to protect them in reserves, but these, too, are dried up and rapidly changing.

A.H.: Peatland and wetland restoration sounds good, but the devil is in the details. How do you define restoration success: how do you know it’s there and not just flooding?

W.K.: It all depends on what goals we set for ourselves and how much the ecosystem has changed. A heavily transformed peat bog cannot be restored in the sense of returning it to its pre-degradation state. Decomposition in this case is a one-way process: peat, when it decomposes, turns into muck, i.e. soil with completely different properties – dried muck even becomes hydrophobic! This is an irreversible phenomenon. And this does not mean that such ecosystems should not be repaired, only it must be honestly said that it will not be possible to recover what was there before the degradation.

Especially since we can do a great deal to improve the functioning of such areas. We can slow down the decomposition of peat and significantly reduce greenhouse gas emissions, and sometimes even reverse the balance towards accumulation. We can also relatively quickly restore these areas as biological filters, that is, get them to start capturing nitrates again – denitrification only requires restoring anaerobic conditions. We can restore them as areas that are very important for water retention. In their marshy state, peatlands perform numerous ecosystem services not only in their area, but their influence extends much wider.

This is due to the fact that peatlands developed in the lowest parts of the land, especially the low ones. They, in a sense, dammed the flow of water in the landscape. Over thousands of years they have accrued to a thickness of a few – a dozen meters, and by that much the drainage base, that is, the level to which water flows from the area, has increased. If we have drained these bogs, they have settled. When, in addition, we keep water in the ditches a meter or two below the surface of the bog, the whole hydrological system is pulled down, so to speak.

All we need to do is to recreate marsh conditions, that is, raise the water level in the ditches more or less to ground level. Or we will eliminate these ditches. Then we will raise the drainage base, and therefore the groundwater level in the areas around us as well. Most of the country is lowland, with gentle slopes, and there are areas adjacent to peat bogs that are only a few meters higher than them. Groundwater in such areas can also be this 1 meter higher. This effect can extend for kilometers. This is a real, spatial impact on nature and agriculture.

The environmental functions and ecosystem services of peatlands extend far beyond their site, provided that water stays close to the surface all year round.

On the other hand, if we are talking about restoring peatlands for vanishing plant and animal species, the situation is more difficult. I, as a botanist, will talk mainly about plants. These species are disappearing because the drained peatland is becoming more and more productive: the amount of biomass is increasing, the light conditions are changing, fast-growing, common plants are beginning to dominate. And, in fact, there is no chance of returning to low fertility conditions so that typical peatland species, such as bog mosses, orchids, woollies or sundews, can grow there. The less a bog is transformed, the greater the chance of success. Therefore, in order to save biodiversity, we need to take care of the fragments that are slightly dry, where the most sensitive and disappearing species are preserved.

It is worth noting that these ecosystems are often not drained by ditches in their own area, but because they are adjacent to heavily drained areas. And this is where an important synergistic effect comes in. If we fix agriculturally drained areas, that is, improve water retention on a larger scale, reduce runoff, improve ecosystem services and reduce carbon emissions, we will, by the way, raise water levels in the landscape so much that this effect will also be felt by the protected – the most naturally valuable – parts of peatland systems.

It should be made clear: most of the ecosystems that should be protected today are merely remnants of what was. True, they still exist as bogs, but most of their area has been reclaimed and cut with ditches. In the popular imagination, bogs are mid-forest enclaves, often high or transitional bogs. Meanwhile, in Poland, they were mostly huge areas in river valleys or in the basins of the land. And this is the clou of the topic of repairing wetlands on a landscape scale, because these small, isolated fragments often cannot be saved without improving water retention on a larger scale.

A.H.: You are the co-author of the Strategy for the Protection of Wetlands in Poland with the Action Plan, which the Ministry of the Environment made available for consultation in February 2026. If you were to explain to a layman what is most important in this strategy: what are the main goals and what is to stop the degradation of wetlands in real terms?

W.K.: There are three main goals in the strategy: one for peatlands, another for other wetlands, and a third for the network of Ramsar sites. On the other hand, the most important thing is why we need such a strategy at all. We want to force cooperation between different sectors of the economy and administration. Wetlands cannot be protected solely by the actions of the Ministry of Climate and Environment. Strategies to date have only been departmental, ministerial documents, but we already know that it is impossible to effectively save wetlands if we limit ourselves to protected areas only.

Wetlands are interconnected vessels, those protected are linked to agricultural and forest areas and watercourse management. And first of all, this cannot be dealt with in one ministry. And secondly, there is already a consensus that this water is needed by the economy. The goal of protecting wetlands is not just to protect nature, but also to protect the country from drought and cities from floods, to reduce the effects of climate change and adapt to it. Added to this is the theme of defense, Shield East and the role of wetlands as a strategic obstacle.

Since there are so many common interests, it is necessary to work together and coordinate activities so as not to interfere with each other. And that is why, for the implementation and adoption of this strategy, a government team was formed. It includes representatives of the Ministries of: Climate and Environment, Agriculture, Infrastructure with Polish Water, National Defense and Finance, but also the General Directorate of Environmental Protection.

Inter-ministerial consultations on the strategy have already taken place, and public consultations are now underway. I hope that the document will not be turned upside down. Most of the assumptions of our project have remained, some have been changed as a result of government arrangements, but for me the key is real cooperation between ministries, especially the participation of the Ministry of Agriculture.

A.H.: So translating that into practice – we’re talking about voluntary, well-paid programs that will realistically encourage farmers instead of forcing anyone to flood their fields?

W.K.: Yes, the programs should be voluntary and financially attractive. No one will force farmers to re-hydrate. On the other hand, it’s worth remembering that they can have concrete benefits from the proximity of re-hydrated peatlands: more stable water levels in the landscape, less drying, and often better conditions for crops.

Peat landowners should be encouraged to raise water levels with subsidies of several thousand zlotys a year. For this we must convince the Ministry of Agriculture, because without this cooperation nothing will be done.

A.H.: The money is there. Since the state pays out drought losses – and sometimes more than 1 billion a year – I find it hard to accept the argument that there are no funds for real incentives for farmers. And today they are, to put it bluntly, weak. Then there’s the problem of ecoschemes, complicated to such an extent that many farmers, especially smaller ones, have no chance to reach for this money.

W.K.: I agree. If support is to work, it must first and foremost be accessible and simple, and the scale of subsidies should match the scale of change we expect. Without this, farmers will not be interested in cooperating. In addition, investment measures are also needed where hydration needs to be physically restored: raising water levels in ditches, reducing runoff, or eliminating drainage. Declarations alone will not sustain the effect on the ground.

Ph. Wiktor Kotowski – biologist dealing with the functioning of wetland ecosystems and the scientific basis of their conservation – especially in the context of climate change mitigation and adaptation. Professor at the Faculty of Biology, University of Warsaw. In addition to his research work, he is socially and professionally involved in nature conservation, including through his activities in non-governmental organizations – he is a founder and board member of the Center for Wetland Conservation, the State Council for Nature Protection, or the Scientific Council of the Biebrza National Park. Wiktor Kotowski was awarded the science popularizer award in the scientist category in 2022 and the badge of honor of the Minister of Climate and Environment in 2025.

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pic. main: Victor Kotovsky