DOI: 10.14393/SN-v32-2020-46916 Received: 06 February 2019|Accepted: 06 February 2020 Assessment of soil loss to vulnerability in the Boane District in Mozambique
Euclides Délio Matule1 Lucrêncio Silvestre Macarringue1,2
Keywords Abstract Boane The soil lost vulnerability study of the landscape units constitutes one of the Stability mechanisms for the design of sustainable land use and cover and natural Geoprocessing resources. Therefore, this research aimed to evaluate the soil loss vulnerability Soil Loss in the Boane district in 2018. The materials used included OLI Landsat 8 and ASTER GDTM V2 images, through which we generated land use and cover and slope maps respectively, soils, lithology, and precipitation databases available in CENACARTA. This data was processed in a GIS environment. The results showed that 53.3% of the district had median stability, 34.7% moderately vulnerable, 11.4% moderately stable, 0.6% stable and 0% vulnerable. These results indicate a favorable situation, but not comfortable at the short term, due to the accelerated rhythm of urbanization and its consequences to the environment that is seen in the last decades, joined to the lack or non- implementation of the main planning plans, that can change this situation in short term.
1Instituto de Formação em Administração de Terras e Cartografia, Matola, Moçambique. [email protected] 2Universidade Estadual de Campinas, São Paulo, Brasil. [email protected]
Soc. Nat. | Uberlândia, MG | v.32 | p.211-221 | 2020 | ISSN 1982-4513 211
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability in Boane District in Mozambique
INTRODUCTION Crepani, et al. (1996). The scale of the vulnerability of basic To analyse a landscape unit, it is necessary to territorial units, from their morphodynamic know its genesis, physical constitution, form characterization, is made according to criteria and stage of evolution, as well as the type of developed from the principles of Tricart's vegetation cover that develops on it. This Ecodynamics (1977). information is provided by Geology, The criteria developed from these Geomorphology, Pedology and Phytogeography principles allow one to create a model where and needs to be integrated to have a faithful he can seek the assessment, relatively and picture of each unit's behaviour towards the empirically, of the stage of morphodynamic occupation. Finally, Climatology needs to help evolution of basic territorial units, assigning us to know some climatic characteristics of the stability values to morphodynamic categories region where the landscape unit is located, to (CREPANI et al., 2001). From this first predict its behaviour towards the changes approximation, a greater variety of imposed by the occupation (CREPANI et al., morphodynamic categories is sought, to 2001). construct a scale of vulnerability for situations The vulnerability to soil loss of landscape that occur naturally (CREPANI, 2001). units is linked to the imbalance in the natural In Mozambique, itinerant agriculture, dynamics of the environment. Each component wood exploitation, firewood and charcoal of the landscape, such as Geology, production and uncontrolled burning are Geomorphology, Pedology, Vegetation, Climate considered the main factors for the reduction and anthropic intervention, participates in of vegetation cover and consequently soil this dynamic in an integrated way. These erosion. components, participate in this dynamic in an The population of Boane uses forest integrated way (DE LA ROSA et al., 2000; LU resources such as pegs, reeds and other et al., 2004; CREPANI et al., 2008). material for house building and they take For Becker and Egler (1997) the advantage of trees for firewood, wood and vulnerability map to soil loss represents the charcoal production, which are the fuels most analysis of the physical and biotic used by the households. Because of this, the environment for the rational occupation and district presents serious problems of sustainable use of natural resources. Its deforestation and soil erosion. association with data of social, economic and In ten years the district has had a political potentiality offers subsidies to population increase of almost 50%. This territorial management (LU et al., 2004). This increase was due to the migration of the vulnerability is analysed from the population from the cities of Maputo and morphodynamic characterization of these Matola, causing the native vegetation cover to units, based on methodologies developed by be removed for the construction of their
Soc. Nat. | Uberlândia, MG | v.32 | p.211-221 | 2020 | ISSN 1982-4513 212
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability
houses. This fact precipitates, at first, the South and Southeast with Matutuine District district vulnerability to soil loss. and the East with Matola Municipality (Figure Pereira and Pinto (2007) state that the 1). It has an approximate surface area of 860 speed and extent with which environmental Km2 and is home to a population of 210,498 problems have been occurring, resulting from inhabitants according to the 2017 Census the intense pressure generated by anthropic (INE, 2017). It is a district with a dry tropical occupation, require the use of data collection climate, with two well-defined seasons, the dry techniques and systematic monitoring of the season (between April and September) and the land surface, compatible with the speed of rainy season (between October and March). these changes. The average annual temperature is 23.7ºC and In recent decades, empirical modelling the average annual precipitation is around 752 techniques associated with geographic mm (MAE, 2005). information systems and satellite imaging The district is crossed by the Umbeluzi, with moderate to high spatial and temporal Tembe and Matola rivers belonging to the resolution have facilitated the monitoring and river basins of the same names, the Umbeluzi quantification of the conditions of changes river being born in the neighbouring e-Swatini occurring on the earth's surface and their (former Swaziland) over a length of 70 km degradation (PONZONI et al., 2014; VIJITH; (MAE, 2005), most important, it is the main DODGE-WAN, 2017). source of potable water for the cities of Maputo Thus, this article aims to assess (capital of the country) and Matola besides vulnerability to soil loss in the Boane district being the main source of water for irrigated in 2018. This analysis will serve as a basis or agriculture. subsidy for the preparation of the different In the past, Boane was dominated by territorial planning instruments (at the forests with high density of tree layer, thick district or municipality level), as well as the trunk trees with wide treetops that rose to a preparation of environmental planning, thus height of 10 to 20m, which was degraded contributing to the production of conservation giving way to pasture and agricultural areas, and preservation measures. with patches of secondary savannah and spontaneous or subspontaneous fruit trees METHODOLOGY (MUCHANGOS, 1999). Boane consists of Jurassic-Cretaceous Location and characterization of the study area basalt material (Volcanic Karroo of the Upper Series), Mananga sediments, pebbles and Boane District is located in the South of alluvial sediments. The basalts are of Maputo Province and borders in the North Jurassic-Cretaceous age, belonging to the with Moamba District in the West and Karroo Super Group, formed during the last Southeast with Namaacha District, in the phase, which of the volcanic emanations called
Soc. Nat. | Uberlândia, MG | v.32 | p. 211-221 | 2020| ISSN 1982-4513 213
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability
Superior Stormberg or Superior Series. These there are also quaternary coverings of sandy basalts are part of the Libombos chain with a materials consisting of alluvial deposits or north-south direction and more than 450km alluvial with gravel, quartz, rhyolites, some long and 20-25km wide and inclined towards minerals and rocks (TIQUE; DYKSHOORN, the east. On both banks of the Umbeluzi River, 1993; VASCONCELOS, 2014).
Figure 1 Location of the study area.
Source: CENACARTA Database (1999).
The relief of the low course of the According to Tique; Dykshoorn (1993), Umbeluzi River basin is characterized, in five main soil units can be found in most parts general, by a slightly undulating landscape of the district: (i) derived from Basalts-Bv; (ii) without great differences in altitude. In the from Mananga with sandy cover of less than North, East and Southwest it presents a 25cm-Ml; (iii) from Post-Mananga-P; (iv) on landscape with small differences of level, rolled Pebbles-S; and (v) alluvial from forming a true plain. The altitude varies from Umbeluzi-F river. 0 to 300 meters (ALBINO, 2012).
Soc. Nat. | Uberlândia, MG | v.32 | p. 211-221 | 2020| ISSN 1982-4513 214
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability
MATERIAL AND METHOD (13-20%); Class E, Strong Wavy (20-45%) and Class F, Mountainous or Escarpment (> 45%) Images from the OLI sensor of the Landsat (RAMALHO-FILHO; BEEK, 1995). satellite, Path/Row 167/78 WRS-2, UTM At the second moment, the analysis and projection, Zone 36S and Datum WGS84 of generation of the thematic maps were made. June 15, 2018, were used; an ASTER GDTM In the case of the soil map, initially the V2 image, acquired through the following nomenclature of soil types was changed (from address: www.earthexplorer.usgs.gov. the FAO classification to the Embrapa The district/country digital cartographic classification) to facilitate the identification of database containing information on the stability values of each soil type, following the following soil, geology and precipitation topics classification presented by Crepani (2001) and on a scale of 1: 1,000,000 was also used for the then the elaboration of the rainfall intensity elaboration of the Soil Loss Vulnerability map. map, elaborated from the relation of the The software ArcGIS 10 was used to annual average rainfall map and the number process the information. of days with rain, transformed into months, The work had several moments. The first that is, by dividing the annual average rainfall was related to the image registration using the by the number of days with rain throughout image/image method because a small the month. displacement of the image was noticed and The third moment was reserved for the subsequently the OLI/ Landsat 8 colour (30m) conversion of the maps from the vector format and panchromatic (15m) images were merged to the matrix (reclassified with the values of to improve their quality, thus obtaining a the stabilities), as well as the arrangement of colour image with 15m of spatial resolution. the database with all the information The area of interest (Boane district) was necessary for the analysis of the ecodynamics. then cut out. The false-colour composition The assigned stability values are shown in 6R5G4B was used to facilitate the Table 1. visualization and choice of samples for The analysis of Ecodynamics (last classification, and the supervised classification moment), served for the preparation of the was chosen using the Maximum Likelihood map of Vulnerability to Soil Loss. The analysis (Maxver) method. In this process, three classes was based on the methodology developed by were created: (i) Vegetation Cover, (ii) Built Crepani et al. (1996) based on the concept of Area and Exposed Soil (since the stability Tricart's Ecodynamics (1977) and the potential value is the same) and (iii) Water. Still at this for integrated studies of satellite images, moment, the slope map was generated with 6 which allow a synoptic, repetitive and holistic classes according to Embrapa criteria: Class A, view of the landscape, to subsidize Zoning Flat (0-3%); Class B, Soft Wavy (3-8%); Class (CREPANI et al., 2008). C, Moderately Wavy (8-13%); Class D, Wavy
Soc. Nat. | Uberlândia, MG | v.32 | p. 211-221 | 2020| ISSN 1982-4513 215
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability in Boane District in Mozambique
Table 1. Stability Values of Types of Landscape Units. Landscape Unity Type Stability Geology Sandstone 2,4 (Lithology) Basic rocks (Gabro) 1,6 Carbonated Rocks (Limestone/Dolimite) 2,9 Acid Rocks (Riolites/Granite) 1,1 Terraces (Unconsolidated Sediments) 3,0 Pluviometric 194,2 (600mm) 1,6 Intensity 226,5 (700mm) 1,8 Vegetation/Land Water 1,0 Use Exposed soils/inhabited area 3,0 Vegetation (Forest Savannah, Mangrove) 1,5 Neossolo Litólico; Neossolo quatzarênico, Neossolo 3,0 Soils Flúvico Cambisssolos 2,5 Argissolos/Nitossolos 2,0 < 2 1,0 2 – 6 1,5 Declivity (%) 6 – 20 2,0 20 – 50 2,5 > 50 3,0 Org.: By the Authors, 2018 from CREPANI et al. (2008).
Once values for all classes of all thematic (Relief/declivity) theme maps were assigned, these maps were S = Vulnerability for the Soils theme integrated using the map algebra technique, Vg = Vulnerability for the Vegetation/soil use generating the Soil Loss Vulnerability Map, theme whose final value resulted from the arithmetic C = Vulnerability for Climate (Rainfall average of the individual values of each theme Intensity) theme using the following equation: RESULTS AND DISCUSSION
Based on the data used in this research, it was
possible to generate thematic maps of the Where: following landscape components: V = Vulnerability of Landscape Unit lithology/geology, slope/geomorphology, G = Vulnerability for Geology theme pedology, land/vegetation cover and R = Vulnerability for Geomorphology rainfall/climate index (Figure 2).
Soc. Nat. | Uberlândia, MG | v.32 | p.211-221 | 2020 | ISSN 1982-4513 216
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability
Figure 2. Classes of the landscape units.
Source: CENACARTA database (1999); OLI Landsat 8 (2018).
The map algebra process allowed us to (Figure 3), thus inferring that the district calculate the average vulnerability value, presents the stages of pedogenesis and obtaining 18 classes of Landscape Units morphogenesis.
Soc. Nat. | Uberlândia, MG | v.32 | p. 211-221 | 2020| ISSN 1982-4513 217
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability
Figure 3. Average Vulnerability Values of Landscape Units.
Org.: By the Authors, 2018.
These average vulnerability values were moderately vulnerable and the values between divided as follows: values between 1 and 1.4 2.6 to 3.0 define vulnerable areas (CREPANI, are considered stable, and those with values 2001). This allowed five categories of between 1.4 and 1.8 were defined as vulnerability to be obtained, namely: Stable, moderately stable. The degree between 1.8 to Median Stable/Vulnerable, Moderately Stable, 2.2 represents the median stable/vulnerable Moderately Vulnerable and Vulnerable class, the values between 2.2 to 2.6 refer to (Figure 4).
Soc. Nat. | Uberlândia, MG | v.32 | p. 211-221 | 2020| ISSN 1982-4513 218
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability
Figure 4. Boane District Soil Loss Vulnerability Map (2018).
Org.: By the Authors, 2018.
The district presents more than half of and is distributed in almost the entire district its area (53.3%) as Median Stable/Vulnerable (Table 2). This area is located in places where
Soc. Nat. | Uberlândia, MG | v.32 | p. 211-221 | 2020| ISSN 1982-4513 219
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability
most of the vegetation cover exists and in This article diagnosed the state of equilibrium clayey soils, with a structure that favours and the natural dynamics of the district's water retention, but that maintains good environment, which constitutes a means for drainage and contains mineral salts in the the design of sustainable practices of land use amount necessary for soil fertility and plant and occupation and natural resources. growth. The results showed the prevalence of a Moderately Stable areas occupy 11.4% median stability (53.3% of the territory), a and are mostly located in areas with situation considered favourable, but we should vegetation, acid rocks and nitossolos. not remain in a comfortable situation because The Moderately Vulnerable area is 34.7% with the pace of urbanisation in recent and is related to the existence of exposed soil decades and its consequences on the due to the opening of new areas for habitation environment in the absence of the and cultivation, as well as the existence of implementation of planning, this situation can Neossolos which are soils with high be put into question, also because there is a topographic factor values, thus constituting a considerable area of moderate vulnerability. considerable risk factor for soil loss (NEVES et The methodology applied has proved to al., 2011). be adequate as the results matched field The stable areas are located along the observations. It is important to draw attention rivers and in the small Libombos reservoir, to the fact that this degree of stability must be constituting less than 1% of the district area, maintained and to the intervention of while the vulnerable areas are tiny, i.e., researchers from the most diverse areas of almost non-existent. knowledge to carry out more studies to guarantee an ecological balance in the district Table 2. Areas of each stability/vulnerability since there are few studies carried out in the Type. country on this matter. Types Area (km2) Percentage
Stable 5.00 0.6 REFERENCES Median 458.00 53.3
Stable/Vulnerable ALBINO, A. J. Bases geoambientais para a Moderately Stable 98.00 11.4 gestão da bacia hidrográfica do rio Moderately 298.00 34.7 umbeluzi-moçambique. Dissertação (Mestrado em Geografia) – UFRJ. PPGG. 2012. Vulnerable BECKER, B. K.; EGLER, C. A. G. Vulnerable 0.05 0.0 Detalhamento da Metodologia para Execução do Zoneamento Ecológico- Total 859.05 100 Econômico pelos Estados da Amazônia Org.: By the Authors, 2018. Legal. Brasília. SAE Secretaria de Assuntos Estratégicos/MMA-Ministério do Meio Ambiente, 1997. CENTRO NACIONAL DE CARTOGRAFIA E CONCLUSIONS TELEDETECÇÃO - CENACARTA. Informação geoespacial sobre Moçambique. 1999. Available
Soc. Nat. | Uberlândia, MG | v.32 | p. 211-221 | 2020| ISSN 1982-4513 220
MATULE; MACARRINGUE Assessment of Soil Loss Vulnerability
in: http://www.cenacarta.com – Access in: Jan do rio Jauru/MT. Soc. nat., Uberlândia, v. 23, 20, 2018. n. 3, 2011. https://doi.org/10.1590/S1982- CREPANI, E.; MEDEIROS, J. S.; AZEVEDO, L. 45132011000300005 G.; HERNANDEZ FILHO, P.; FLORENZANO, PEREIRA, L. H.; PINTO, S. A. F. Utilização de T. G.; DUARTE, V. Curso de sensoriamento imagens aerofotográficas no mapeamento remoto aplicado ao zoneamento ecológico multitemporal do uso da terra e cobertura econômico [CD-ROM]. In: Simpósio vegetal na bacia do rio Corumbataí – SP, com o Brasileiro de Sensoriamento Remoto, 8. suporte de sistemas de informações Salvador, 1996. Anais. São Paulo: Image geográficas. XIII Simpósio Brasileiro de Multimídia, 1996. Sensoriamento Remoto. Anais…, CREPANI, E.; MEDEIROS, J. S.; HERNANDEZ, Florianópolis, Brasil, 21-26 abril 2007, INPE, P.; FLORENZANO, T. G.; DUARTE, V.; p. 1321-1328. 2007. BARBOSA, C. C. F. Sensoriamento Remoto PONZON, I F. J., MACARRINGUE, L. S., e Geoprocessamento Aplicado ao SANTOS, S. L. dos; SANTOS-JÚNIOR, J. L. Zoneamento Ecológico-Econômico e ao Comparação entre fatores de reflectância Ordenamento Territorial. São José dos gerados a partir de dados dos sensores Campos. SAE/INPE. 2001. TM/LANDSAT 5 e MODIS/TERRA aplicando CREPANI, E.; MEDEIROS, J. S.; PALMEIRA, diferentes metodologias de conversão de dados, A. F.; SILVA, E. F. Banco de Dados Revista Brasileira de Cartografia, No. 66/2: Geográficos dos Municípios de Gilbués e p. 263-270, 2014. Monte Alegre do Piauí (pi) (Municípios RAMALHO-FILHO, A.; BEEK, K. J. Sistema de pertencentes ao núcleo de desertificação avaliação da aptidão agrícola das terras. de Gilbués).INPE. São Jose dos Campos, 3. ed. Rio de Janeiro: EMBRAPA-CNPS, 1995. 2008. SILVA A. M. da; SILVA M. L. N.; CURI N.; DE LA ROSA D.; MORENO J. A.; MAYOL F.; AVANZI J. C.; FERREIRA M. M.; Erosividade BONSÓN T. Assessment of soil erosion da chuva e erodibilidade de cambissolo e vulnerability in western Europe and potential latossolo na região de lavras, Sul de Minas impact on crop productivity due to loss of soil Gerais, R. Bras. Ci. Solo, v. 33, p. 1811-1820, depth using the ImpelERO model. 2009. https://doi.org/10.1590/S0100- Agriculture, Ecosystems and 06832009000600029 Environment, 81, p. 179–190, 2000. SUCUPIRA, P. A. P. Indicadores de https://doi.org/10.1016/S0167-8809(00)00161-4 degradação ambiental dos recursos EMBRAPA SOLOS. Available in hídricos superficiais no Médio e Baixo :
Soc. Nat. | Uberlândia, MG | v.32 | p. 211-221 | 2020| ISSN 1982-4513 221