MONITORING ACTIVE FIRES IN THE LOWER PARANÁ RIVER FLOODPLAIN: ANALYSIS AND REPRODUCIBLE REPORTS ON SATELLITE THERMAL HOTSPOTS

Floodplain wetlands play a key role in hydrological and biogeochemical cycles and comprise a large part of the world's biodiversity and resources. The exploitation of remote sensing data can substantially contribute to monitoring procedures at broad ecological scales. In 2020, the Lower Paraná River floodplain (also known as Paraná River Delta, Argentina) suffered from a severe drought, and extended areas were burned. To monitor the wildfire situation, satellite products provided by FIRMS-NASA were used. These thermal hotspots – associated with active fires – can be downloaded as zipped spatial objects (point shapefiles) and include recent and archive records from VIRRS and MODIS thermal infrared sensors. The main aim was to handle these data, analyze the number of hotspots during 2020, and compare the disaster with previous years' situation. Using a reproducible workflow was crucial to ingest the zip files and repeat the same series of plots and analyses when necessary. Obtaining updated reports allowed me to quickly respond to peers, technicians, and journalists about the evolving fire situation. A total of 39,821 VIIRS S-NPP thermal hotspots were detected, with August (winter) accounting for 39.8% of the whole year’s hotspots. MODIS hotspots have lower spatial resolution than VIIRS, so the cumulative MODIS hotspots recorded during 2020 were 8,673, the highest number of hotspots of the last 11 years. Scripts were written in R language and are shared under a CC BY 4.0 license. QGIS was also used to generate a high-quality animation. The workflow can be used in other study areas.

Long-term analysis of River Tisza water level data with regard to the ecological water demand of floodplain water bodies

One of the main threats of our time is the increasing water demand not only globally, but also locally. These are often met at the expense of ecological water demand, jeopardizing the structural and operational conditions necessary to maintain good ecological status in aquatic and wetland habitats. This is why it is of great importance to explore possible water retention options. In 2019, based on the long-term data series on the water level of River Tisza, we studied the frequency and extent of flooding in the floodplain between Tiszabercel and Gávavencsellő, where there are valuable wetlands, including a ‘sanctuary’-type backwater. This was necessary because recently the floodplains have undergone negative changes. Their water volume has gradually decreased, their valuable wildlife has become rarer, some of them have completely dried out in the autumn and even one of them has burned out. From the analysis of the examined 48-years data, it could be concluded that flooding was relatively frequent in the sampled area, but the extent of water coverage had no significant effect either in space or time. It was also found that only water levels above 700 cm (based on the water meter of Tiszabercel, 98.36 mBf) could adequately ensure that the water bodies are filled up and flushed out. However, there is little chance of this, because of four reasons: (1) water levels of this height are becoming rare; (2) the duration and height of high water levels are mostly short in time; (3) water levels of several water bodies are artificially decreased; (4) the drainage effect of the River Tisza – which has been significantly incised after the river regulation – prevails in the area. Due to all, in the future, there would be a great need to maintain the water levels in the floodplain wetlands as efficiently as possible after the floods – for which we have made specific proposals for the places and methods to preserve the ecologically necessary amount of water.

The Beautiful and the Dammed: Defining Multi-Stressor Disturbance Regimes in an Atlantic River Floodplain Wetland

Natural hydrological fluctuations within river floodplains generate habitat diversity through variable connections between habitat patches and the main river channel. Human modification of floodplains can alter the magnitude and frequency of large floods and associated sediment movement by interrupting these floodplain connections. The lower Wolastoq | Saint John River and its associated floodplain wetlands are experiencing anthropogenic disturbances arising from climate change, increased urbanization in the watershed, changing upstream agricultural landscape practices, and, most notably, major road and dam construction. By comparing digitized aerial images, we identified key periods of change in wetland extent throughout an ecologically significant component of the floodplain, the Grand Lake Meadows and Portobello Creek wetland complex, with significant erosion evident in coves and backwater areas across the landscape following dam construction and significant accretion around the Jemseg River following highway construction. Connectivity and hydrological regime also influenced other habitat components, namely nutrients and metals retention, as well as the composition of the local macrophyte community. These findings address two key aspects of floodplain management: (1) understanding how hydrological alteration has historically influenced floodplain wetlands can inform us of how the ecosystem may respond under future conditions, such as climate change, and (2) the mechanisms by which habitat diversity and disturbance regimes filter biological communities, with the potential for patches to host a rich biodiversity continuously supporting critical ecosystem functions.

Alternanthera sessilis (sessile joyweed).

A. sessilis is a pioneer species typically growing on disturbed areas and in wetland habitats, and regarded as a fast-growing highly invasive weed. It is adapted to grow on a range of soil types ranging from poor sandy or alkaline soils, to loam or black cotton soils. It is also able to grow in seasonally-waterlogged areas as well as in areas with extreme dry conditions (Holm et al., 1997). A. sessilis can be found invading floodplain wetlands, margins of rivers, streams, canals, ditches, ponds, reservoirs, tanks, marshes, swamps, wet low-lying ground, ephemeral pools, seasonal pans and damp forest. This species is also a weed in fields with sorghum, millet, Eleusine spp., maize, cotton, cassava, cereal crops, pastures, and vegetable farms (Gupta, 2014). Consequently, this species has been listed as invasive in India, South Africa, Namibia, Spain, Hawaii and many other islands in the Pacific Ocean (see distribution table for details). It is also listed as a noxious weed in the United States (USDA-NRCS, 2014).