Costanera Sur Ecological Reserve occupies more than three hundred hectares between Puerto Madero and the Río de la Plata and forms one of the largest natural landscapes within Buenos Aires. Lagoons, reed beds, grassland, young woodland, trails and viewpoints developed across reclaimed ground later colonised by plants and wildlife. Its identity depends on that unusual history: a city expansion project became a protected ecological system through succession, sedimentation and changing hydrology.
The interior lagoons are among the principal habitats. Their water levels change with rainfall, evaporation and connections with lower wet areas. During wetter periods, open water reflects sky, reeds and birds; in drier phases, mudflats, emergent vegetation and exposed ground become more prominent.
Reed beds form dense vertical masses around shallow water. Their stems slow currents, retain sediment and provide cover for fish, insects and birds. Colour shifts from strong green to ochre and brown as the seasons change and older growth dries.
Grassland covers broad open surfaces. Grasses and herbaceous plants move visibly with the wind and create a landscape of changing height and texture. Seeds, flowers and stems support pollinators, small mammals and birds using open habitats.
Scrub marks a denser stage of plant succession. Shrubs, climbers and young trees create transition zones between grassland and woodland. These areas demonstrate how one group of plants changes light, soil and moisture conditions for the communities that follow.
Young woodland has developed across more stable sectors. Willows, alders, ceibos and other species create shade, leaf litter and a strong vertical structure. Trunks and crowns form environments that contrast sharply with the exposed grasslands and reflective lagoons nearby.
Birdlife is one of the most visible features. Herons, coots, ducks, raptors, woodpeckers and many smaller species use water, mud, grassland and woodland. The close arrangement of habitats allows very different behaviours to be observed within one reserve.
Insects provide a less obvious but essential ecological network. Dragonflies, butterflies, bees, beetles and other groups contribute to pollination, decomposition and food chains. Their activity changes with temperature, flowering and moisture.
Reptiles and amphibians occupy wet edges, sunny ground and sheltered vegetation. Their movement is generally discreet and strongly dependent on weather. Temporary pools and damp ground create feeding and reproductive habitats after rain.
Mammals such as coypu and smaller species use grassland, water margins and wooded sectors. Tracks, burrows and feeding signs reveal their presence even when the animals themselves remain hidden.
Trails cross the reserve through wide earth and gravel routes. Some pass through exposed grasslands, others enter woodland or run beside lagoons. Changes in shade, wind and sound make the diversity of habitats perceptible through movement.
Viewpoints open across water, vegetation and skyline. Reeds and birds dominate some views; from others, the glass towers of Puerto Madero rise behind the woodland. This overlap is one of the reserve’s most characteristic visual contrasts.
The former Costanera Sur promenade adds another historical layer. The area once functioned as a major riverfront recreation zone when the shoreline lay closer to the city. Later reclamation shifted the relationship among avenue, bathing area and river.
Puerto Madero keeps the metropolitan context constantly visible. Towers, roads and former docks stand only a short distance from mud, reeds and wildlife. The reserve therefore never feels detached from the city, even in its most enclosed sectors.
The outer edge connects directly with the Río de la Plata. Sediment, waves, wind and fluctuations in water level reshape the shoreline and deposit branches and organic material. The reserve belongs to a much larger estuarine system rather than functioning as an isolated park.
Light changes the landscape continuously. Sun produces strong reflections on lagoons and backlighting through grasses; cloud softens the tones; late-afternoon light turns towers, reeds and birds into overlapping silhouettes.
Seasonal drought and fire have also shaped the site. Grassland can change rapidly and later regenerate, leaving sectors of different height, colour and composition. Disturbance forms part of the ecological history rather than being separate from it.
Costanera Sur Ecological Reserve is defined by the transformation of artificial ground into a varied ecological mosaic. Lagoons, reed beds, grassland, woodland, birds and skyline form an inseparable whole. Its distinctive quality lies in preserving evidence of both the city’s expansion into the river and the ability of natural processes to create new habitat at the metropolitan centre.