Wet season connectivity among aquatic habitats in the northeastern Amazon

In the northeastern Brazilian Amazon, the rains have been easing off after several months of regular heavy downpours, interspersed by drizzle or light rain, and an occasional dry, sunny day. Signs of flooding are everywhere. In the image above, the lake spills over a dirt road. In the water, small fish dart rapidly from one side of the flooded road to the other. The water then flows down along a normally dry, sandy track, forming a temporary stream to the left. The flow passes the village and meets another, larger dirt road and follows that along one side until it soon joins a permanent stream. Featured image above: Lago do Povo (“Lake of the People”), Bragança in June 2019.

Despite the the dirt roads, built some 35 years ago, which cross the wetlands known as Campos, or (flooded) “Fields”, water manages to reconnect again different aquatic habitats. In the past, the flooding must have been spectacular. I was told that people from the Campos used to arrive by canoe to the city. Today, people still use canoes to get around the Campos.

A canoe (chained to a post) in the Bom Jardim area of the Campos wetlands near Bragança in June 2019. The canoe filled with rainwater and sank. The excess water is easily sloshed out by vigorously maneuvering the canoe from side to side.
A family travelling in a canoe at Bom Jardim, Bragança in April 2009.
Part of northeastern Pará state in Brazil. Dark areas: water, dark blue areas: mangrove forest, light blue areas: terrestrial or riparian forest and lighter green or yellow areas: disturbed habitat, agriculture or urban areas. The Campos is the dark area (center), the Caeté river runs north/northeast (right) and the city of Bragança is the large light green/yellow area on the left margin of the Caeté river. Landsat L5 TM 2008-06-20 222-061 images were used to create this RGB 754 composite using the GNU package Quantum GIS .

Rainfall in the northeastern Amazon is strongly seasonal, most of which falls between January and May, after which there is a steady decline to the driest period between September to November. However, there is also much inter-annual variation due to effects of the El Niño Southern Oscillation in the Pacific and sea surface temperature variation in the Tropical Atlantic. There are also longer term changes in rainfall due to deforestation, which has severely altered natural vegetation cover in the northeastern Amazon.

Seasonal pattern of rainfall in the northeastern Brazilian Amazon. Data are from Tracuateua station, 15 km west of Bragança, and represent the period October 1972 to April 2019. Graph created with ggplot2 using GNU-R.

Useful links

Barichivich, J et al. 2018. Recent intensification of Amazon flooding extremes driven by strengthened Walker circulation. Science Advances 4(9): eaat8785. https://doi.org/10.1126/sciadv.aat8785

Mayta, VC et al. 2019 The role of the Madden–Julian oscillation on the Amazon Basin intraseasonal rainfall variability. International Journal of Climatology 39(1): 343-360. https://doi.org/10.1002/joc.5810

Zemp, DC et al. 2017. Fewer trees mean less rain for the Amazon basin. Geophysical Research Letters 44(12): 6182-6190. https://doi.org/10.1002/2017GL072955

The Intercept_ https://theintercept.com/2019/07/06/brazil-amazon-rainforest-indigenous-conservation-agribusiness-ranching/

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