Petreza: The Floodplain Attica Cannot Afford to Lose

The floodplain of the Rafina Megalo Rema stream; looking upstream. The trees punctuating the green thickets of Reed Cane and rushbeds are nearly all Salix alba, a rare riparian woodland stand for Attika (drone photo from: https://megalorema.gr/).

 Petreza: The Floodplain Attica Cannot Afford to Lose

Hidden between the towns of Spata and Pikermi, remains one of the last free-flowing streams in Attica. This is the main stem of the Rafina Megalo Rema, as if flows through part of the Mesogeia Plain, this is the Petreza floodplain. 

Along the river's main channel, as it exits the entrenched reach of the Attiki Odos Highway,  lies Petreza, one of the region's last natural river floodplains and arguably one of the most valuable yet overlooked landscapes for nature conservation in the Athens Metropolitan Area. Far more than a rare patch of open green space, Petreza is a living ecosystem that supports exceptional biodiversity.  Although parts of the area may benefit from legal protection (on paper that is...), this unique floodplain is now under imminent threat from a large-scale river engineering project that proposes to transform much of the natural river into a heavily channelized flood-control corridor. The project, costing just over 100 million Euros is now underway - buldozers tearing down trees... If implemented in its totality, the project could irreversibly alter one of Attica's last functioning river ecosystem landscapes.

Floodplains are the areas where rivers naturally expand during periods of high flow. Rather than being "unused land", they act as natural reservoirs, slowing floodwaters, storing carbon, filtering pollutants and recharging groundwater. Across Europe, scientists increasingly recognise that protecting and restoring floodplains is among the most effective and cost-efficient ways of reducing flood risk while simultaneously conserving biodiversity.

The Petreza reach represents one of the largest remaining floodplain systems of the Rafina Megalo Rema, one of the few largely free-flowing rivers left in the Athens Metropolitan Aegion. Its riparian woods, wetlands and seasonally flooded habitats support remarkable wildlife, including around 150 recorded bird species, numerous freshwater fish, including lots of European Eels (Critically Endangered!), amphibians, reptiles (a populations of Stripe-necked Terrapins) and a museum-full of aquatic invertebrates. Several habitat types found here, including white willow (Salix alba) riparian woods mixed with rush beds (Juncus spp), are now exceptionally rare in Attica.

Beyond its ecological importance, Petreza provides essential ecosystem services for people. By remaining connected to the river, the floodplain naturally attenuates flood peaks before water reaches downstream urban areas. It also improves water quality, supports groundwater recharge and contributes to local climate regulation during increasingly frequent heatwaves. These benefits are precisely why the European Union now promotes Nature-based Solutions as a cornerstone of modern water management.

Today, however, Petreza is a battle ground between the government-promoted project for flood control and environmentalists, including concerned scientists. My colleagues at HCMR have written technical letters asking for this project to stop. It must be re-designed as a Nature based Solutions project that will protect key natural areas such as Petreza. The conflict is over design and implementation of the proper flood-control infrastructure, we are not against a project, we strongly disagree with the kind of project. Scientists have expressed concern that disconnecting the river from its floodplain, removing riparian vegetation and replacing natural riverbanks with hard engineering structures (gabion held levees) will totally degrade ecosystem functioning, reduce biodiversity and compromise many of the ecosystem services that make the floodplain valuable. Instead of eliminating floodplains, current European practice increasingly favours working with natural river processes rather than against them. So our Greek project is anachronistic, poorly planned, haphazard, and plain stupid! 

The choice facing Petreza - and the Greek Government agencies that support this- is therefore much larger than a local planning issue. It reflects two contrasting approaches to flood management: one based primarily on traditional high-cost engineered channels, and another that combines flood protection with ecosystem conservation through Nature-based Solutions.

As climate change brings more intense rainfall and hotter summers to the Mediterranean, preserving natural floodplains like Petreza is becoming not only an environmental priority but also an investment in public safety and long-term resilience. Once these ecosystems are lost, they are extraordinarily difficult—and often impossible—to restore.

Saving Petreza means protecting one of Attica's last living river landscapes, ensuring that future generations inherit a river capable of supporting both nature and people.

After more than 30 years working in river and wetland conservation, I am convinced this project could have been designed very differently. Destroying one of Attica's last natural floodplains is a choice—not a necessity.

Visit the environmentalists website to find out more (https://megalorema.gr/). 

We at HCMR (Inland Waters) support the environmental campaign to STOP the engineering project under way on the Rafina Megalo Rema Stream.

The upper Petreza floodplain, looking upstream from a drone image in early spring. Newly leafed white willow (Salix alba) line the anastomosing stream banks, while extensive seasonally flooded rush meadows stretch beyond the stream banks in the floodplain. This exceptional mosaic of riparian woodland and wet meadow habitats is unique and survives here on a scale found nowhere else in the peninsula of Attika (drone photo by Emmanuil Sperelakis/HCMR 8th March 2019).

The upper part of the Petreza floodplain; drone photo looking upstream. Early spring photo shoing recently leaved Salix alba (green trees) and the extensive high thickets of reed cane (drone photo by Emmanuil Sperelakis/HCMR 8th March 2019).

The lower, last part of the Petreza reach near the Arionos Bridge, here looking down-river towards the Arionos road and the eventual confluence of the main-stem with the Valanaris tributary (drone photo by Emmanuil Sperelakis/HCMR 8th March 2019).

The lower, last part of the Petreza reach near the Arionos Bridge, here the river enters a shallow valley, in the distance the Etos Hill (drone photo by Emmanuil Sperelakis/HCMR 8th March 2019).

White willows (Salix alba) forming loose stands along the river (at center). This spot is near the upper part of the floodplain (Near the Pyrgos Petreza Winery, downstream of the Pekermi-Spata bridge). In late summer 2026 this stream-side dirt road was built and many trees were felled. Photo: Sept. 2026.  

Walking along the river after flood waters enter the fields and rushbeds.  Photo: late May 2026.

Much of the Petreza reach is thick with these towering reed cane thickets (Arundo donax). Photo: late May 2026.

In late spring the walk on the small road along the right side of the Petreza reach is wonderful. A naturalists paradise.  Photo: late May 2026.

The Petreza is an important hotspot for birdlife; being located right next the the Loutros Spata hotspot it hosts well over 150 bird species, including many rare migrants. One the threatened migrants is this Turtle Dove. Photo: late May 2026.

Fish abound in most parts of the Petreza reach of the river especially in the upper and mid floodplain areas. Eels are very common and they probably feed on these small schooling fishes; these being Rhodes Minnows (Ladigesocypris ghigii), translocated from Rhodes and now well established.  Photo by Antonis Lazaris. 

We know very little about the biodiversity of this area. One of Antonis Lazaris's students documented the existance of the Stripe-necked terrapin in the stream at the Petreza floodplain. 

The catchment of the river basin of the Rafina Megalo Rema stream. In red outline the main-stem strech known as the Petreza reach where the exceptional floodplain habitats are located (base-map from Karymbalis et al. 2021). 

Location map of the Petreza Flood plain area (map: sketch deliniation by S. Zogaris on recent Goole Earth images). 

A map of protected area designations in the immediate area. The yellow zone is Zone B2 of Moderate Protection of Landscapes and Archeological Sites (Z.O.E. Mesogeion). Part of the floodplain of Petreza is within this designation.

Petreza, the lower part of the main stem of the Rafina Megalo Rema stream is a distict water body, monitored by HCMR under EU policy mandate (WFD 2000/60). Currently its ecological status is assessed aat Moderate. 

Newspaper Headlines: Documento (Sunday, 26 July 2026): Flood Control Project Leaves Rafina Exposed to... Flooding.  Scientists and local residents highlight the risks and policy failures of the project on the Megalo Rema Stream. 

Resources

HCMR's recent statement on issue:

Assessment_of_the_Ecological_Significance_of_the_Petreza_Floodplain_Rafina_Megalo_Rema

In the News: 

https://www.efsyn.gr/periballon/1446984/sos-gia-kindyno-plimmyras-sti-rafina-i-proeidopoiisi-toy-elkethe-gia-to-megalo-rema/

Bibliography:

https://megalorema.gr/en/rafinas-great-river/

Karymbalis, E., Andreou, M., Batzakis, D.-V., Tsanakas, K., & Karalis, S. (2021). Integration of GIS-Based Multicriteria Decision Analysis and Analytic Hierarchy Process for Flood-Hazard Assessment in the Megalo Rema River Catchment (East Attica, Greece). Sustainability, 13(18), 10232. https://doi.org/10.3390/su131810232

European Environment Agency (2019). Floodplains: a natural system to preserve and restore. EEA Report No. 24/2019.

European Commission Joint Research Centre. Nature-based Solutions for Water Management.

Penning, E. et al. (2023). Nature-based solutions for floods, droughts and biodiversity: Do we have sufficient proof of their functioning? Cambridge Prisms: Water.

Papadaki, C., Dimitriou, E., Skoulikidis, N. et al. (2023). Regarding the river engineering project being implemented at Rafina Megalo Rema stream. Hellenic Centre for Marine Research.https://www.researchgate.net/publication/385420330_Regarding_the_river_engineering_project_being_implemented_at_Rafina_Megalo_Rema_stream_in_Greek

Zogaris S, Charmpila EA, Vukić J, Giakoumi S, Barbieri R, Zogaris D, Ašenbrenerová E, Viñuela Rodríguez N, Tarkan AS and Šanda R. 2023. Unnoticed introductions, a silent threat for biodiversity: island endemic Ladigesocypris ghigii (Actinopterygii, Leuciscidae) translocated to continental Greece. The European Zoological Journal, 90(2), pp.840-855.

Zogaris S, Papadaki, C., Stoumboudi, M. (2026, Aug.). Assessment of the Ecological Significance of the Petreza Floodplain (Rafina Megalo Rema River) and the Compatibility of the Proposed Engineering Interventions with European Water Resources and Flood Risk Management Policy (In Greek). Assessment_of_the_Ecological_Significance_of_the_Petreza_Floodplain_Rafina_Megalo_Rema

Our Collaborators at Universidade Federal Rural do Rio de Janeiro

Our collaborators in Rio! 

Part of the reasoning for our recent August trip to Brazil was meeting like-minded researchers. This time, we were hosted by Professor Karine Bueno Vargas and her husband Claudio Nuernberg Junior at the Federal Rural University of Rio de Janeiro (UFRRJ). Professor Karine spearheads biogeographical and landscape studies at the Department of Geography and is interested in our landscape assessment methodology - LAP index - and our use of indices for assessment, climate adaptation and for educational training. Karine is doing some fantastic work in promoting biogeography including such interdisciplinary applications. She is vice-president of the Ibero-American Society of Biogeography (Sociedad Iberoamericana de Biogeografía) and on the board of directors of the Brazilian Association of Biogeography (Associação Brasileira de Biogeografia). 

It was wonderful to visit the univeristy campus at UFRRJ at Seropédica, on the outskirts of Rio de Janeiro. This is definately one the largest university grounds in South America and features specialized research laboratories and extensive training areas, botanical gardens etc. Complete with huge open landscapes with much livestock and especially many horses! (Estamos no Brasil!). We did some birding one very rainy afternoon and also walked in the field the following morning. It was really fascinating to be able to see the campus, its artificial lakes and wetlands, meet students and opportuniteis for fruitful collaboration here. 

I present some snapshots of our short visit to - UFRRJ and our natural history trips nearby (in Rio and the surrounding coast). We really feel so much gratitude for being able to live such an experience. Being in Brazil was a dream come true for us.

Photos from the University 

Vassiliki with Karine and students at the lab. Note the Brazilian Neo-colonial architecture in the background.

Next to our accommodations at the very nice Hotel Escola - UFRRJ we had wonderful views of the school's horses and stables and the countryside. The Unviersity was founded in 1910 as a college for agriculture and veterinary medicine, establishing agricultural education in Brazil. These early roots have shaped its focus and direction ever since.

These are African oil palms creating an interesting cultural landscape. 

The capybaras are very friendly here. They are overlooking the Lake of Istituto do Agronomia; Lago do IA (which I though was.... Artificial Inteligence...IA in Brazilian). 

Lago do IA (22°45'31.6"S 43°41'41.7"W). The largest artificial waterbody on campus, a real hotspot for birds. Of course we suggested it as on on eBird and got it official. 

Huge roost of cattle egrets (garça-vaqueira) at Lago de IA. 

Of course, the ''flamingo-coloured spoonbill'' (colhereiro) - Roseate Spoonbill. 

White-faced Whisltling Ducks (Ireré), these we have seen in Africa too. 

Of course, all those nasty ticks (carrapatos) are handled by this bird, an immature Yellow-headed Caracara (carrapeteiro) on a sleeping Capybara.

In 11 days of travel in Brasil we saw only three wild mammal species and very few signs of wild mammals near habitation (could this be due to over-hunting?). But the Capybara is abundant, even in urban settings. Despite the ''scare'' associated with their ticks. 

The campus was full of parrots! This one is one of the commonest, the White-eyed Parakeet - Periquitão-Maracanã (Photo I took at further afield at Itatiaia). 

Nice to meet Brazilian students! 

The main building - Pavilhão Central - and surrounding landscape. The university has an area of approximately 3024 hectares, making it one of the largest such university ground in Latin America. On the right you see Lago de IA which we suggested as an eBird hotspot! (photo by Drone Carioca https://www.youtube.com/watch?v=OuwVOA8G8eo)

Rio De Janeiro

Spent just two rainy nights in Rio. Big marvellous city - want to go back!

Cristo Redentor! On the last day, the morning sun finally shone and we got this pic! This is an emblem of Rio - Christ the Redeemer; it was completed in 1931, an art-deco statue 30 meters proud on a mountain peak 700 meters high. Of course, it faces East.

Rainy Rio - the Center of Town. We found a fantastic restaurant here and also visited a bookstore.

First time in Copacabana...Everybody is here! 

 You must go for the sunset at Pedra do Arpoado.

Pedra do Arpoado.

Later, some yoga at Pedra do Arpoado (very stormy)

And the moon over Copacabana beach.

Further afield - River and Riparian Habitats (Paraty - Ubatuba)

Near Rio and Sao Paulo there is the Mata Atlantica area with a distictive semi-diciduous tropical forest (and with subtropical highlands). Many areas are easily accessible, some are important eBird hotspots. People are very kind and welcoming and very talkative and interested in what you are doing. The biodiversity in the streams and riparian zones is amazing.

Small creek at Fazenda Angelim at Ubatuba (23°23'38.0"S 45°03'54.1"W).

Catfishes, of the Corydorases, Subfamily Corydoradinae. Ubatuba.
 

The culvert bridge of Reinaldo Mateus (23°18'15.9"S 44°52'09.2"W). This is a definate problem for migratory fish dispersal. 

The Ubatumirim river (where the bridge was, above). Typical Mata Atlantica river.

The Ubatumirim river. 

Drizzle on the docks of the canal of Paraty.

Rio Itamambuca, southwards, on the coast (23°24'09.0"S 45°00'41.8"W). The Tropic of Capricorn is approximately at 23°26′ S of the Earth's equator. 

Lobster Claw Heliconia (probably Heliconia bihai) on the trail near hotel on the Itamambuca.

Rio Itamambuca; we stayed nearby for four nights. 

Itamambuca estuary (23°24'25.2"S 45°00'36.2"W).

Brazil: With André Tostes at Salesópolis

Birding is really important for nature conservation. I say this because I think birding is the best way to promote public natural history participation! Brazil is a country of amazing contrasts, inspiring conservation efforts and catastrophic environmental degradation often occur side by side. Just a few days ago, we returned from a trip to this remarkable country, meeting people and exploring places for the first time. Here, I will riff on the importance of birding in Southeastern Brasil, from our views during our mini-road trip through São Paulo, Rio de Janeiro and Minas Gerais states. On this post I concentrate on one such destination near São Paulo and our guide there.

First, our guide and the birding scene in Southeast Brazil 

Of course, I want to thank my newfound friend and top birding guide André Tostes, who introduced us to the Salesópolis area. This took place on our second day in Brazil, of our 11-day road trip. His guidance was a trip highlight! First, I present some details of his bio and notes on the birding scene in Southeastern Brazil.

André Tostes is a 35-year-old Brazilian birding guide, a family man, and someone genuinely in love with nature. He is of the arts, with a business and letters degree and a tour guide certificated by the Tourism Ministry. He has been actively birding since 2017 and uploading pics and sounds since 2018, contributing to iNaturalist, Wikiaves and eBird. His major area of deep nature experiance is his home state of São Paulo, with particular knowledge of the Atlantic Forest (Mata Atlantica) and southeastern Brazil in general. He has an amazing knowledge of the regional specialties and difficult-to-detect birds. His field skills include bird identification by both sight and vocalization, locating secretive forest and marsh species, bird photography, and sound recording. I was especially impressed by his persistence in bringing birds out by careful playback and his remarkable ability to find and identify birds by sound. And since André is also a master of languages—his own language and an expert English-language teacher as well—he is a great help for someone trying to learn Brazilian Portuguese! (I am listing André's address below - I highly recommend his guiding services for English-speakers in Brasil).  

Now something important for us english-speakers traveling in Brazil...If you don't speak Brazilian Portuguese, it is really a culture-shock to do an independent road-trip there. People speak their language, and many of course understand or speak some Spanish as well. It is not a touristy country and English is not widely understood. So to break-into the philosophy of the culture it is interesting and I think important to take up some Portuguese; I did and I enjoyed it. (I recommend a 30-day AI assisted multi-media blitz; also using Pimsleur® while drving, Youtube, and other such media; i.e., listen-repeat while commuting and keeping a notebook. Also, limited duolingo as well. The key is building confidence in speaking!).

Back to birding: I should mention that in very recent years, birding is growing strong in southeastern Brazil. I was told there are important events and a growing number of young specialists, not just eclectic photographers or jungle-hermit museum men. A birder is now known here as a passarinheiro (Informal community slang) or more formally observador/a de aves. The nationwide movement and social media hashtag used by local birders is #vempassarinhar ("come birdwatching"). Key citizen science hubs are: a) WikiAves, the absolute central hub for Brazilian citizen science, seemingly nearly every serious birder in Brazil uses this platform to upload photos and vocalizations; and b) Avistar: The largest annual birdwatching festival and gathering in Latin America, held in the greeny city of São Paulo. On Youtube media a very interesting channel for listening to the wonderful Brazilian language, about birds specificially, is Planeta Aves hosted by Willian Menq (https://www.youtube.com/@PlanetaAves). Also, have a look at the top-notch touring work promotion done by Calyptura Expeditions (https://www.youtube.com/@CalypturaExpeditions), shout-out and thanks to Brazilian birding veteran,  Rene Santos for his help in our trip preparation. 

The Salesopolis in São Paulo State: a new eBird hotbed of hotspots!

The tiny town of Salesópolis is known to birders worldwide primarily because it is home to one particularly rare bird, the São Paulo Marsh Antwren, and because of a small ecolodge that regularly hosts visiting birders, Macuquinho Lodge (providing feeders and a trail). The very small town of Salesopolis, not really a polis, is located only a couple of hours (91 kms) from the main international airport of São Paulo (Guarulhos). Our birding experience here, however, was somewhat different, since we toured the wider area without focusing exclusively on the rare birds and without visiting the well-known lodge. And we did not find the rare Antwren - Formicivora paludicola (also classified as a subspecies Formicivora acutirostris paludicola). It is very obvious that you don't need either of these two attractions to enjoy and explore Salesópolis as a premier birding and natural history area. There is so much more to see and discover.

One of the highlights was actually discovering a new eBird hotspot at our own guesthouse accommodation, Pousada Quintal de Hortênsias, just outside the town. We highly recommend the place for at least a three night stay. It is full of birds, with a short upland trail through secondary woodland and immediate access to a tiny stream floodplain. It has wonderful landscape views, but is not yet...geared to focusing on avitourism (no feeders, unfortunately). But the place has mega-potential, and it is also wonderfully situated for exploring a variety of other birding sites in the surrounding countryside. We evaluated the bird richness of the property and, within just two days, identified at least 60 bird species there. André then helped promote the site as an eBird hotspot and discussed with the proprietor some simple improvements that could make the property even more attractive to birders and other nature-going visitors.

For me, this is an important part of what birding can contribute to conservation. Promoting small, locally owned accommodations, documenting their biodiversity, and encouraging nature-based tourism can give local communities another reason to appreciate and protect the landscapes around them. We really believe that this kind of small-scale ecotourism and birding promotion can contribute to the conservation of the wider landscape around Salesópolis.

Salesópolis--Salesópolis Wetland

Salesopolis wetland, a huge area with open-country birds and wonderful road-side vistas. The farms nearby also present interesting open-country birds, very close to the town of Salesopolis.

Brazilian Teal. 

Yellow-throated Spinetail.

Black-headed Donacobius, these one's are at Pousada Quintal de Hortênsias.

Rufous Tiger Herons at the wetland.

Masked Water-Tyrant, another common bird, looks very much like a wheatear! 

Guira Cuckoo, a common species in open country and parks as well.

Marvellous wetlands! 

Early morning it was chilly! 

Salesópolis--Pousada Quintal Das Hortansias 

One of the nicest places a birder can stay at: Pousada Quintal Das Hortansias). 

The pousada with the native woods above. 

Nice trail above the pousada, regenerating native woods. 

Blond-crested Woodpecker, seen twice on our trip, this one was from further afield, but I got a similar view at the trail above the pousada. 

The view near the trail within the property of the pousada. View of the landscape east of town. Note the extensive eucalypt and pine plantations in the distance. 

Red-breasted Toucan. Surprisingly this is the only species we saw really well. We heard another two and saw one of those fly-over, but in 11 days we only say one decent toucan. I am so happy we took this photo.

Campos Flickers. 

Rufous-sided Crake, seen breifly (and filmed) after much play-back persistance. 

Black-headed Donacobius; amazing marshbirds on display.

Guans are not easy to see in a rural landscape where they are frequently hunted. On one of my early morning walks I saw some above the guesthouse. This photo is from Ubatuba on the coast (touristy place, where they are totally fearless of humans).

 

Sapphire-spangled Emerald. One of several hummers seen. 

Serra do Mar State Park--Núcleo Padre Dória

The guards and the paperwork upon entering Serra do Mar State Park--Núcleo Padre Dória. No one else was there, no fee to pay (just pre-book). Nice situation. 

Perhaps the best raptor of the entire trip: Black Hawk-Eagle (Spizaetus tyrannus).

One of the amazing bromeliads. 

One of the tigerwings we saw. Not much butterfly activity, it was still "late winter" in the area. 

Seeing birds in the forest was not easy. Trogons, we heard them many times, did not see a single bird. 

In good company.

Salesópolis--Bairro dos Mirandas

André Tostes, a natural optimist, working on his skills at playback. 

Bare-throated Bellbird: several were singing and easily visible from a far. One of the best birds of the trip. 

Sooty Tyrannulet, seen really well. 

  

Please inquire about at:

André Tostes: https://www.instagram.com/tostesandre/

And birders should visit Pousada Quintal das Hortênsias, find information at: https://pousada-quintal-das-hortensias.allsaopaulohotels.com/en/

This graffiti was found at the base of a bridge near Ubatuba: A bird that wants to fly needs no cage....

And our final eBird contributions in our 11-day trip from Sao Paulo to Rio and back again: 40 lists, 178 species identified, 144 photographed. Slow birding during a road-trip with many other obligations, not just birding. You may be surprised at the rather low overall number of birds. Birding needs time and lots of patience. A reason to go back!