Study proposes criteria to help delimit and conserve Cerrado wetlands

No fewer than eight important hydrographic basins depend on the ecosystems that make up the Cerrado, Brazil’s savanna-like biome, but ambiguities in the legislation have permitted the advance of soybean plantations in the region. The warning is in an article by Brazilian researchers in the journal Perspectives in Ecology and Conservation.

By José Tadeu Arantes  |  Agência FAPESP – The Cerrado is the most endangered of Brazil’s major biomes, and the part known as the Cerrado wetlands is especially vulnerable. These wetlands feed perennial streams, supplying no fewer than eight of Brazil’s 12 hydrographic regions. The sources of the Xingu, Tocantins, Araguaia, São Francisco, Parnaíba, Jequitinhonha, Paraná and Paraguay, among other important rivers, are in the Cerrado. Destruction of the wetlands not only threatens the biodiversity and outstanding beauty of the landscape in the Cerrado but also endangers the nation’s water and energy security.

The wetlands are also an outstanding carbon sink, storing more than 200 metric tons per hectare. Changes in their cyclical balance tend to release methane, a major greenhouse gas, into the atmosphere.

The definition of wetlands is confusing, however, and this has been exploited by big landowners, who not only convert dry areas of the Cerrado into cropland but are also lobbying for the chance to drain the wetlands in order to expand their already vast soybean plantations. Quite apart from other objections, from the strictly economic standpoint, they would be shooting themselves in the foot since the possibility of irrigation depends on survival of the water sources.

To clear up the confusion and offer decision-makers sound scientific criteria, a group of Brazilian researchers has produced an article on the many ecosystems encompassed by the wetland concept. The article is published in the journal Perspectives in Ecology and Conservation.

“The lack of precise definitions has undermined the regulatory framework and left a significant proportion of the Cerrado unprotected. We set out to clarify the concept of wetlands, specifying the ecosystems that can be so classified, analyzing their dynamics, and offering proposals for their protection,” Giselda Durigan, first author of the article, told Agência FAPESP.

Durigan is a researcher at the Institute of Environmental Research (IPA), an arm of the São Paulo State Department of Infrastructure and Environment, and a professor in the graduate studies programs of São Paulo State University (UNESP) and the State University of Campinas (UNICAMP). She has studied the Cerrado for more than 35 years.

“An example of the serious harm that can be done by the lack of precise definitions and the ambiguities in interpreting the law is Resolution no. 45, passed on August 31, 2022, by CONSEMA, the Environmental Council of Mato Grosso,” she said. The Cerrado covers almost 40% of Mato Grosso state. “Disrespecting a decision of the Federal High Court [STJ], this resolution regulated the ‘environmental licensing of activities and business ventures located in wetlands’ within the state. Despite the euphemisms, it simply authorized destruction.”

Durigan made a point of providing a precise definition. “Wetlands are areas of continental land subject to periodic or permanent flooding or waterlogging. Given their fragility and extreme importance to water storage and filtration, they are globally protected by the intergovernmental treaty adopted at Ramsar in Iran in 1971. Brazil signed the Ramsar Convention in 1996 but has so far failed to fulfill its commitment to map all of its wetlands,” she said.

Brazil has coastal wetlands, where tidal flows cause flooding by saltwater or brackish water, and two hydrologically distinct types of wetland far from the coast: floodplains and swamps (várzeas and pantanais) periodically flooded by overflowing rivers; and land that is temporarily or seasonally inundated by a rise in the water table.

“Most wetlands in the Cerrado are the latter. The heavy rains that fall in the summer months slowly seep down into the soil, recharging the water table and accumulating in wetlands, which are the source of streams that never dry up and flow into Brazil’s great rivers even in dry periods. In this respect, the Cerrado is quite unlike other savannas around the world, where the major rivers dry up completely for much of the year,” Durigan said.

Full protection

The confusion that undermines the regulatory framework, she added, is largely due to the existence of several types of vegetation in the Cerrado wetlands, with many different local names such as campo úmido (wet grassland), campo de murundus (termite savanna), turfeira (bogland), vereda (palm swamp), palmeiral (palmland), buritizal (Mauritia palm grove), gallery forest, and so on. Two or more types may coexist in a single wetland area, from grassland to dense forest – hence the difficulty of understanding the Cerrado wetlands, let alone delimiting and protecting them.

“The law sometimes refers to one of the types, as in the case of veredas in the Native Vegetation Protection Law [Law 12,651/2012], leaving all the other types unprotected. Or it protects only part of a wetland, leaving entire swathes without legal cover,” Durigan said.

The article resulted from a multidisciplinary effort, she said, involving specialists in vegetation, hydrology, ecophysiology, conservation, restoration and environmental legislation, who used their knowledge and practical experience to unify and disseminate their understanding of the matter.

The group received support from FAPESP via three projects (19/07773-1, 20/09257-8 and 20/01378-0).

“We argue that all wetlands should be equally and fully protected by law, guaranteeing that they won’t be converted to cropland and that their natural flood or inundation pulses aren’t affected by land uses in adjacent areas. Sustainable land management practices, such as beekeeping and forest resource harvesting, for example, can be allowed but must be validated and regulated,” Durigan said.

This precautionary approach is justified by the main threats to the Cerrado wetlands, such as damming of watercourses, drainage, urban expansion, infrastructure construction projects, and uncontrolled extraction of water from wells for irrigation of crops and eucalyptus plantations in entire hydrographic basins where the original vegetation was not forest.

“All these activities are highly impactful. They lower the water table and may even deplete it locally, endangering water security and ecosystem services in the Cerrado. This must be stopped urgently by competent legislation and enforcement,” Durigan said.

The Native Vegetation Protection Law, she added, deals with wetlands in a confusing way, leaving part of them as Permanent Conservation Areas (APPs in the Portuguese-language acronym) or Restricted Use Areas (AURs). Some types of wetland in the Cerrado do not match the definitions in the law, undermining enforcement with judicial, social and political conflicts.

“In an effort to pacify the situation, the STJ decided that, given their indubitable environmental importance, all wetlands should be assumed to be protected, whether as APPs or AURs, regardless of nomenclature. This was the decision disrespected by the resolution passed by CONSEMA in Mato Grosso,” she said.

The good news is that right now a large group of technicians and scientists representing different regions of Brazil are working hard to produce a National Inventory of Wetlands, under the leadership of specialists Wolfgang Junk and Cátia Nunes da Cunha, of the National Science and Technology Institute for Wetlands (INAU), to provide support for the Ministry of the Environment.

“The legend ‘Wetlands’ has recently been included on the maps produced by MapBiomas, which is a big step forward,” Durigan said, referring to the collaborative network of non-governmental organizations, universities and tech startups established to map land use and land cover in Brazil. “However, demarcating wetlands in the field at the scale of rural properties is no easy task, and this hinders enforcement of the law. Our article puts forward objective criteria based on hydromorphic soil, endemic flora and maximum elevation or minimum depth of the water table to facilitate delimitation of wetlands at the local level.”

The article “Cerrado wetlands: multiple ecosystems deserving legal protection as a unique and irreplaceable treasure” is at: www.sciencedirect.com/science/article/pii/S2530064422000384?via%3Dihub.