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Abstract

Urbanization in the Concepción metropolitan area (36° S) has historically impacted valuable ecological areas such as wetlands and lagoons. We built indicators to analyze disturbance of biodiversity in six urban wetlands. We propose three measures: a Naturalness indicator and two indicators for Plants and Macrolepidoptera species richness. Multiple regression models were developed for the assessment of indicators. Results show that the wetlands with the lowest degree of human interference are located in a protected area and surrounded by a matrix of semi-natural landscape, whereas the more disturbed ones are closer to urbanization. Results indicate that Macrolepidoptera richness is more affected by the distance to roads, in contrast with the richness of plants, which is affected by housing density. A tool for the prevention of loss of species and the conservation of these ecosystems in urbanized areas is generated.
Carolina Rojas Q
Department of Geography University of Concepción
Einer Sepúlveda
Department of Zoology, University of Concepción
Olga Barbosa
Institute of Environmental and Evolutionary Sciences
Carolina Martínez
Department of Geography, Pontical Catholic University of Chile
Octavio Rojas
Center of Environmental Sciences, University of Concepción
Annual Meeting of American Geographer, , Chicago Illinois, EE.UU, April 21-26 - 2015
Urban Patterns and Biodiversity in Urban Wetland
Abstract
Urbanization in the Concepción metropolitan area (36° S) has historically impacted valuable ecological areas such as wetlands and lagoons.
We built indicators to analyze disturbance of biodiversity in six urban wetlands. We propose three measures: a Naturalness indicator and two
indicators for Plants and Macrolepidoptera species richness. Multiple regression models were developed for the assessment of indicators.
Results show that the wetlands with the lowest degree of human interference are located in a protected area and surrounded by a matrix of
semi-natural landscape, whereas the more disturbed ones are closer to urbanization. Results indicate that Macrolepidoptera richness is more
affected by the distance to roads, in contrast with the richness of plants, which is affected by housing density. A tool for the prevention of loss of
species and the conservation of these ecosystems in urbanized areas is generated.
Keywords: Wetlands, Urbanization, Biodiversity, Naturalness
Introduction
- In the last decades, the tendency has been to concentrate world population around coastal areas, estimating that currently, close to 50% of
the world’s urban population lives within 60 Km from the coast.
- Coastal cities present alteration processes in the ecosystem function of the environment, landscape degradation, and socio-environmental
conicts.
- Coastal urbanization has drastic consequences such as: landscape homogenization, alteration of natural processes such as nutrient and
energy ow, habitat degradation, loss of biodiversity - at the cost of local and natural heritage.
- Wetland biotypes with delicate ecological equilibrium and complex composition and structure, sustain hydrophyte vegetation and maintain
water-saturated substrate, and for that reason are some of the most affected environments by urbanization.
- Wetlands are situated among the most biologically productive, are important sources of biological diversity, water reservoirs, and are re-
sponsible for a high primary productivity based on the trophic chains of the organisms.
- Wetlands provide distinct ecosystem services, such as: purication of pollutants, ood mitigation, aquifer recharging, and mitigation of ero-
sive processes.
Figure 1: Ecosystem Services
- Wetlands situated in the city are more relevant given that their provision of ecosystem services has a direct effect on more people.
- Urban wetlands in the city provide carbon sequestration, microclimatic regulation, rainwater drainage and recreation.
- Urban wetlands easily degrade with anthropic interventions (e.g. dumping of residual wastes, backlling, accumulation of trash and green
waste, among others). The result is a profound deterioration of the nutrient and energy cycles, generating a decrease in species diversity and
an increase in species that are tolerant to pollution.
Objectives
- Analyze the disturbance in wetland biodiversity due to distinct factors of urbanization.
- Evaluate the use of different biodiversity indicators to determine the degree of wetland disturbance.
Study Area
The study area corresponds to six wetlands located in the Concepción Metropolitan area (2.830 km2), located in the coastal zone of the VIII re-
gion of Biobío (Latitudes 36º to 38º South). These coastal wetlands are 1) Laguna Verde; (2) Parque Central; (3) Lorenzo Arenas; (4) Rocuant-
Andalién; (5) ,Sector Cuatro Esquinas; (6) Lenga.
Results
Biodiversity Indicators
Model 1
Presents a global t of R2 = 0.57, indicating that the richness of plants is inuenced by the variables of urbanization. In agreement with the
standardized coefcients, housing density (0.75) has a greater inuence than distance to motorways (0.13), and the percentage of urbaniz-
able area (0.20). The three variables have a positive inuence, and at the same time that they increase in the wetland matrix, plant richness
increases given the larger number of introduced species.
Model 2
Presents a global t of R2 = 0.76, indicating that the richness of macrolepidoptera is inuenced by the variables of urbanization. According to
the standardized coefcients, the distance to roads (-0.69) has a more signicant inuence than housing density (-0.38), and the percentage
of urbanizable area (-0.18). The tree values have a negative inuence, and for that reason when they are increased in the wetland matrix, the
probability of macrolepidoptera richness decreases.
Model 3
Presents a global t of R2 = 0.88, indicating that it is capable of reasonably explaining how the naturalness of the matrix is inuenced by the
variables of urbanization. In accordance with the standardized coefcients, the percentage of urbanizable area (0.4) has a signicant and posi-
tive inuence on the indicator of naturalness. Meanwhile, housing density (-1.0) and the distance to roads (-0.2) are affected negatively. For this
reason, while the urbanizable space is still not built, the indicator of naturalness is higher, because the ground cover is maintained. In the case
of distance to roads and housing density, while they decrease, the probability remains higher of an increase of naturalness.
Conclusions
- The indicator of naturalness is a good predictor of urbanization patterns on wetlands.
- Wetland surface area has decreased 40% since 1975, being substituted by disperse vegetation and later by urbanization, causing environ-
mental quality loss.
- Wetlands with a lesser degree of disturbance are Laguna Verde and Lenga, considering that Laguna Verde is located within a natural re-
serve Hualpén and surrounded by a matrix dominated by native forest. Meanwhile, Lenga is close to this reserve, within a shing pier with low
urbanization.
- Laguna Verde and Lenga present a higher richness of macrolepidoptera, principally because of the decrease of anthropic effects related to
urbanization and the scarce presence of introduced ora. This is a critical factor that determined the differences between these ecosystems,
and those immersed in urban areas.
- The wetlands Lorenzo Arenas, Parque Central and Rocuant – Andalién presented a lesser richness of macrolepidoptera and a higher pres-
ence of introduced ora, patterns which directly affect the diversity of macrolepidoptera, decreasing at the same time that the variables of ur-
banization increase.
- Vegetational heterogeneity is increased because of the great number of introduced species associated with systems with higher levels of
urbanization.
- Urbanization variables that most affected wetland biodiversity are housing density and distance to roads.
- The urbanizable area of the wetland has the largest effect on the naturalness of the classes of the land use of the wetland.
- Loss of biodiversity of the Wetland Rocuant-Andalién is worrying, given that the condition of its ecosystem is relevant for the associated bird
migration, as well as rainwater drainage – which is an extremely important function in this territory, due to its reoccurring ooding periods.
Acknowledgements
FONDECYT N°1150459
FONDAP CONICYT N °15110020.
Proyect VIRD 214.603.015-1.0. Efectos de la Urbanización en la conservación de la biodiversidad de humedales costeros” (2014-2015)
Figure 2: Wetland locations Map
(1) Laguna Verde
(2) Parque Central
(3) Lorenzo Arenas
(4) Rocuant-Andalién
(5) Sector Cuatro Esquinas
(6) Lenga.
Methods
- Three indicators were used to evaluate the biodiversity of the wetland matrix: (i) Macrolepidoptera spe-
cies richness, (ii) richness of species and plants; and (iii) Index of Naturalness of the matrix.
- The biodiversity indicators are evaluated through multiple regression models that utilize independent
variables as distinct geographical factors of urbanization.
Seven predictor variables that correspond to typical geographic factors at an urbanization level, these are:
- % Urbanized surface
- Number of Land Uses
- Population Density
- Housing Density
- Distance to Roads
- % Urbanizable Surface
- NDVI Normalized Vegetation Index
The best explicative model resulted in being the one that retained the variables Percentage of urbanizable
area, Housing density and Distance to roads.
2
1
3
6
4
5
Microclimate
Regulation Air Purifying Noise
Reduction
Drainage
Rainwater
Open
Spaces
Treatment
Sewage
URBAN WETLANDS
Ecosystems Services
Wetlands Indicator of Naturalness Richness of Plants Richness of Macrolepidoptera
Rocuant Andalien 0,36 5
Parque Central 0,07 8 19
Lorenzo Arenas 0,04 12 19
Laguna Verde 0,67 5 44
8
Lenga 0,43 4 20
Sector Cuatro
Esquinas
0,18 9 11
DEPENDENTS VARIABLE MODELS
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