Human activities degrade hippopotamus homes at Bui National Park, Ghana

Researchers found that the number of hippopotamus in the Bui National Park declined by about 70% after the construction of a hydroelectric dam in the reserve.

The Bui National Park is one of the few areas where the common hippopotamus resides in Ghana. The combined resources of the Black Volta River and the abundance of grasses make the area very suitable for hippopotamus. However, in an attempt to solve the electricity crisis the country faced in 2007, the government of Ghana constructed a hydroelectric dam in the heart of their home.

Farmers clearing trees along the rivers to begin cultivation at Bui National Park.

Knowing the consequence of dam creation on aquatic species, scientists Godfred Bempah, Martin Kobby Grant, Changhu Lu, and Amaël Borzée from Nanjing Forestry University, China, wanted to understand how the hippopotamus, a mega semi-aquatic species, was impacted by this project. The results have been published in the journal Nature Conservation. Assessing the impact of the dam construction can advise policy and decision making in future projects like this.

The researchers spent 24 days (2 days per month for 12 months) at the Bui National Park to estimate the number of hippopotamus individuals and understand local migratory activities, as well as to assess changes in land cover in the area after the dam was constructed. They then compared this information with historical data to understand the ecological changes within the area.

A hippopotamus in the Zoologico de Vallarta at Mismaloya south of Puerto Vallarta, Mexico. Photo by David Stanley under a CC BY 2.0 license

To complement the field surveys, the researchers spoke to local people familiar with the reserve before and after the dam construction. These included fishermen, canoe operators and park rangers. During the interactive discussion, all of them stated that the numbers of hippopotamus have declined compared to periods before the dam construction. They attributed the decline to poaching and habitat destruction.

The results indicated a decline in hippo numbers of about 70%: from 209 individuals in 2003 to 64 individuals in 2021.

A seized skull of Hippopotamus amphibius at the Bui national Park.

The study revealed noticeable changes in land cover after the dam construction, and, most importantly, a decline in forest cover, as well as destruction of riparian grasses, the habitat preferred by the hippopotamus. The increase in water levels flooded the areas where the animals used to reside, forcing them to disperse to other suitable areas. As they dispersed, the animals became vulnerable to poaching, which combined with habitat loss eventually led to a decline in hippopotamus numbers. It is possible that some of the animals might have successfully moved to other areas outside the reserve.

The hippopotamus is listed as Vulnerable to extinction by the IUCN Red List of Threatened Species.

In conclusion, the authors note that the number of common hippopotamus individuals in the park has declined following the dam construction, in connection with habitat destruction and poaching. Once these threats are removed, the hippopotamus can survive in the medium to long term, when effective management plans are implemented.

Research article:
 

Bempah G, Kobby Grant M, Lu C, Borzée A (2022) The direct and indirect effects of damming on the Hippopotamus amphibius population abundance and distribution at Bui National Park, Ghana. Nature Conservation 50: 175-201. https://doi.org/10.3897/natureconservation.50.87411

A decade of monitoring shows the dynamics of a conserved Atlantic tropical forest

Characterised with its immense biodiversity and high levels of endemism, the Atlantic Tropical Forest has been facing serious anthropogenic threats over the last several decades, demanding for such activities and their effects to be closely studied and monitored as part of the forest dynamics.

Cattle farming, expanding agricultural land areas and mining have reduced the Atlantic Forest to many small patches of vegetation. As a result, important ecosystem services, such as carbon stock, are steadily diminishing as the biomass decreases.

Brazilian researchers, led by Dr. Écio Souza Diniz, Federal University of Viçosa, spent a decade monitoring a semi-deciduous forest located in an ecological park in Southeast Brazil. Their observations are published in the open access Biodiversity Data Journal.

The team surveyed two stands within the forest to present variations in the structure and diversity of the plants over time, along with their dynamics, including mortality and establishment rates. They based their findings on the most abundant tree species occurring within each stand.

At the forest stands, the most abundant and important species for biomass accumulation are concluded to be trees larger than 20 cm in diameter, which characterise advanced successional stage within the forest.

“It is fundamental that opportunities to monitor conserved sites of the Atlantic Forest are taken, so that studies about their dynamics are conducted in order to better understand how they work,” note the scientists.

“The information from such surveys could improve the knowledge about the dynamics at anthropised and fragmented sites compared with protected areas.”

In order to encourage further research into the composition, diversity and structure of the Atlantic Forest over time and the subsequent contributions to the preservation of this threatened ecosystem, the authors made their data publicly available. The datasets, including species occurrences, are now openly accessible via the Global Biodiversity Information Facility(GBIF) and the biodiversity informatics data standard Darwin Core.

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Original source:

Diniz ES, Carvalho W, Santos R, Gastauer M, Garcia P, Fontes M, Coelho P, Moreira A, Menino G, Oliveira-Filho A (2017) Long-term monitoring of diversity and structure of two stands of an Atlantic Tropical Forest. Biodiversity Data Journal 5: e13564. https://doi.org/10.3897/BDJ.5.e13564