Abstract :
[en] The study of land use land cover change (LULC) provides a measure of how landscapes are transformed to meet the natural resource needs of humans. Unraveling how land use constrains biodiversity and ecosystem functions, to determine the consequences of global change for mountain ecosystems, is critical for landscape planning and management to supply vital ecosystem services to millions of upland and lowland inhabitants. This understanding is particularly important for assessing impacts on tropical mountain ecosystems, where altitudinal and climatic gradients can produce sensitivities in ecosystem responses and affect the long-term provision of services and the well-being of associated human populations.
Given this issue, this research aimed to further the understanding of the impacts of land use changes on mountain systems of Northern Ecuador. To achieve this goal, we tested an adapted version of the Driver-Pressure-State-Impact-Response (DPSIR) framework for tropical mountain systems. Within this framework, I conducted an ecosystem assessment in a representative mountainous landscape of northern Ecuador with the following specific objectives: 1) characterize spatio-temporal patterns of land use, 2) reveal driving forces for the land use transitions, 3) analyze the effects of land use change on local biodiversity, ecological functions, and ecosystem services, and 4) evaluate if land use change affects the capacity to supply ecosystem services.
The study region comprises the territory of the canton of Pedro Moncayo, located in the Andean province of Pichincha, and encompasses 332 km² distributed among five parishes. It is a landscape with climatic conditions, and land use legacies characteristic of the highlands of northern Ecuador. The territory has a wide altitudinal gradient ranging from 1900 to 4000 m.a.s.l. and it encompasses a mosaic of different natural ecosystems and distinct land uses which can be described following the altitudinal gradient. The higher altitudinal zone (above 3300 m) is dominated by native ecosystems, represented by páramo and highland montane forests. The middle altitudinal area (2800-3300 m) has been extensively used for agriculture and livestock over time, causing severe soil degradation, and the lower lands are characterized by shrub-dominated dry ecosystems.
First, land use change dynamics characterized by Markov chain transition probabilities along elevation and geographic gradients revealed clear patterns. A significant expansion of floriculture (13 times) and urban areas (25 times) was found, reaching together almost 10% of the territory from 1990 to 2014 on previous agricultural land located at lower elevations in the east of the studied territory. Our findings also revealed an unexpected high probability of persistence (between 0.75 and 0.9) of páramo, but also a 40% reduction of montane forests, with the lowest probability (<0.50) of persistence in the elevation band of 2800-3300 m where agricultural land is replacing this land use and land cover (LULC) class at higher elevation. These trends highlight the threat of permanently losing the already vulnerable native mountain biodiversity. The LULC trends detected were integrated with publicly available geospatial and temporal data for socio-economic factors, demographic, infrastructure variables, and environmental parameters into a generalized additive models (GAMs). GAMs of socio-economic factors, demographic, infrastructure variables, and environmental parameters explained between 21 to 42% of the variation of LULC transitions observed in the study region, where topographic factors were the main explanatory variable for most of the models.
Second, using the soil health framework, I assessed the impact of native forest conversion to anthropic systems (planted forests, pastures, and monocultures) on soil fertility and biodiversity conservation in the highlands of northern Ecuador. The biological dimension of our assessment focused on the diversity, abundance, and biomass of edaphic macroinvertebrate communities as proxies for soil functions. The soil invertebrate communities and soil chemical parameters were studied in topsoil samples using 25×25×10 cm monoliths, obtained from ten sampling sites randomly selected in the reference and the anthropic systems. Our results showed that native forests presented greater values for richness, evenness, and diversity of soil macroinvertebrate communities than the other land use categories, demonstrating a significant loss of taxonomic biodiversity at order and genus levels after forest conversion to anthropic environments. This piece of research also found a significant reduction of trophic diversity in native forests converted to anthropic environments. The results from the soil chemical parameters also confirmed the distinction in soil health between native forests and anthropic environments. Our results highlight the risk associated with current trends of native forest loss and conversion to managed systems in high mountain ecosystems in the tropics, illustrating how these alterations could cause biodiversity loss and degradation of the chemical parameters of soil fertility.
Third, in relation to the effect of LULC changes on microclimate, native forests provided more sTable environmental conditions, where significantly lower temperatures and higher relative humidity values were documented than the other land use types. This effect on microclimate was significantly explained by the highest temperatures at intermediate levels of gap fraction, which represents the amount of light radiation reaching the lower stratum of a forest serving as a proxy for vegetation cover differences among land uses. In addition, native forests provided a buffer effect on the variations in mesoclimate, defined as climatic processes occurring at a scale of tens to hundreds of kilometres, whereas local temperature variations registered on human altered systems (planted forests and pastures) were significantly explained by the mesoclimate variation, except for monocultures that exhibited a mismatch between the two scales of climate. These results highlight the importance of native forest for microclimate regulation, an ecosystem service which can act synergistically with other biodiversity conservation goals to sustainably manage landscapes in tropical Andean Mountain systems (Chapter 4).
Fourth, in relation to the temporal change in the distribution of ecosystem services in the studied territory, clear patterns of distribution were detected both spatially and temporally. A decrease in the provision of food was observed precisely where urban infrastructure has been extended, in the east of the territory. Whereas in the southwestern part of the territory, in addition to the higher elevations of all the parishes, a higher value was detected for regulatory and cultural ecosystem services (Chapter 5).
Finally, I consider that the proposed DPSIR framework and its practical implementation is a good alternative for conducting ecosystem assessments that could be replicated in other tropical mountain landscapes. This framework could help develop sound land management plans that could prevent broad scale, irreversible ecosystem degradation. This phase was initially implemented by sharing our major findings with local authorities and stakeholders. However, more effort is needed to link the research insights gained from our study with local implementation and to guide decision making processes.
