ABSTRACT
The increasing loss of wetlands at the global scale demands immediate response by improving management practices and ecological restoration. When people degrade wetlands, environmental restoration must overcome biotic and economic barriers that can be considerable. We assessed the floristic composition of a wetland subjected to anthropic disturbances and expansion of invasive species, then compared our results with historical data from 2005 to 2015. The result revealed that changes in floristic composition and dominant native and invasive dominant species occurred during this 16-year period. In the dry season, we found significant differences in species richness between the years 2005 and 2021, with a significant reduction in species richness in the latter year. This loss of species richness represents an unfavorable change in the floristic composition trajectory, which we explain as an effect of sustained anthropic disturbance. Floristic data from the rainy season was not conclusive. Typha domingensis, and the invasives Phragmites australis and Festuca arundinacea have been favored by disturbances and increased their cover at the expense of other wetland species, reducing the wetland’s floristic diversity. Our objective was to redirect the floristic composition trajectory in the La Mintzita wetland by proposing management strategies for controlling the above-mentioned species based on three ecological restoration strategies: biocultural (targeting simultaneously the loss of biodiversity and of traditional use of Typha), productive (to control expansion of P. australis which has no traditional use in the region, we propose a new use), and ecocentric (to control F. arundinacea and recover native species cover).
Redirecting the ecological trajectory to increase diversity is necessary for the restoration of degraded wetlands subject to anthropic disturbances.
The strategic implementation of different approaches to ecological restoration represents an opportunity for the rehabilitation of complex ecosystems in periurban contexts where human presence is a driver of environmental change.
In our study area, a biocultural approach is possible because cattail has been used for centuries, but other approaches are needed for historically recent plant invaders.
Since 1900, according to Davidson (2014), the world has lost between 64% and 71% of its wetlands. In that same period, Mexico suffered a similar loss or deterioration of over 62% of its wetland surface (Landgrave and Moreno-Casasola 2012). Wetlands—areas in which water is the main controlling factor of the environment and its associated plant and animal life (Ramsar 2016)—are transitional zones between terrestrial and aquatic ecosystems where the water table is generally at or near the land surface, or where the ground is covered by shallow water (Cowardin et al. 1979). Wetland ecosystems harbor a rich diversity of plants and animals that participate in the maintenance of their intrinsic processes, such as freshwater supply, food production, water filtration and cleaning, sediment retention, and nutrient cycles like those of nitrogen and phosphorus (Tabilo-Valdivieso 1999, Mitsch and Gosselink 2000).
Wetlands are characterized as plant communities in which plant species are tolerant to anoxic soil conditions. Based on such tolerance, hydrophytes are classified into obligate or facultative wetland species (Rodríguez-Arias et al. 2018). Obligate wetland species are good indicators of the environmental condition of these ecosystems because they are easy to identify, and because they respond to changes in the hydroperiod, water chemistry, type of substrate, landscape connectivity, edge effects, and perturbation regime (Hernández et al. 2015). Therefore, it is technically feasible to obtain information about wetland conservation status through long-term monitoring of the vegetation. This information can be used for designing adaptive management practices (Sah et al. 2014).
The floristic composition of wetlands partially determines their functioning. In turn, floristic composition depends on environmental conditions like climate, resource availability, and perturbation regime, all of which might be altered by anthropogenic causes (Brun et al. 2012). Changes in environmental conditions often lead to changes in the dynamics of floristic composition and its trajectory. Consequently, the modifications of an environmental controlling factor, like fire or herbivory dynamics, might gradually deteriorate the community’s resilience and drive it through a threshold with an abrupt change in species composition (Sah et al. 2014).
Ecological restoration functions as a tool for redirecting species composition trajectories and aids the recovery of degraded, damaged, or destroyed ecosystems (Society for Ecological Restoration 2004). Restoration can help to conserve and replenish the ecosystem’s natural capital and services (Kumar 2011). There are different approaches to restoration. Depending on the socio-ecological context and expected use of the restored site, three main categories have been discussed in the literature: biocultural, productive, and ecocentric restoration (Jordan and Lubick 2011, Lyver et al. 2016, Chang et al. 2019). Together, these different approaches provide a mosaic of opportunities for the rehabilitation of complex ecosystems, to which they must be strategically applied in combination.
Biocultural restoration is based on the reciprocal relationships between humans and nature. Restoration management strategies designed following the biocultural approach allows incorporation of either historical or contemporaneous relationships between the local human communities and the ecosystem (Kimmerer 2013, Kurashima et al. 2017, Chang et al. 2019). Beyond the rehabilitation of degraded landscapes, biocultural restoration might also support the renovation and strengthening of cultural practices and identity, including the resurgence of language and the connections of people with places, something that can be fundamental to promote the resilience of the socio-ecological system (Kurashima et al. 2017, McMillen et al. 2017, Pascua et al. 2017, Bremer et al. 2018, Winter et al. 2018).
Productive restoration rehabilitates some elements of structure and function of the original ecosystem through sustainable productivity of the ecosystem. The objective of productive restoration is to recover structure and function of the ecosystem and at the same time extracting resources that generate economic benefits for the local populations (Ceccon 2013, Borda-Niño et al. 2016).
Finally, ecocentric restoration prioritizes the benefit to nature itself, which implies that human interests—or even needs—have a secondary character (Ceccon and Pérez 2016). This approach is based on the principle of respect for the intrinsic value of nature (Clewell 2000, Swart et al. 2001) and is focused on the re-creation of a previously existing ecosystem (Jordan and Lubick 2011).
La Mintzita is a spring-fed wetland with a rocky-stony bottom offering diverse habitats (Ramírez-Herrejón et al. 2013) which is located south of the city of Morelia (Michoacán, Mexico). It provides 40% of the drinking water consumed in the city and provides refuge to endemic plant and animal species (Gámez and Lindig-Cisneros 2014). Because of its location in the periurban area of the city, the La Mintzita wetland is subjected to diverse anthropic disturbances, the most impactful being water extraction, fires caused by agricultural burning in adjacent parcels, and overgrazing. These disturbances have generated a vegetation mosaic with areas dominated by native species and other areas dominated by invasives (Escutia-Lara et al. 2009, Ramírez-Herrejón et al. 2013). Consequently, the application of different restoration approaches is needed in different areas of the wetland complex.
The vegetation in La Mintzita is dominated by three species: Typha domingensis (southern cattail, locally known as tule), Phragmites australis (common reed or carrizo), and Festuca arundinacea (tall fescue; pasto, or zacate festuca). Common reed and tall fescue are both invasive species in the wetland system. The southern cattail and common reed predominate in permanently flooded sites and tall fescue is dominant in occasionally flooded areas and in the border of the wetland that is adjacent to terrestrial habitats.
In the past decades, T. domingensis has expanded its distribution and has become more abundant in wetlands throughout the world—especially in North America—due to anthropogenic alteration of wetland hydrology and nutrient load (Bansal et al. 2019). Increased nutrient loads have been reported for La Mintzita (Ramsar 2012) and coincide with Typha expansion in these wetlands (Rodríguez-Arias 2018). A major consequence of the dominance of T. domingensis is the loss of species richness (Lawrence et al. 2017). In Western Mexico, particularly in Michoacán, wetlands have been used as a source of Typha and Schoenoplectus leaves for making different products since precolonial times, and nowadays their management by local actors mediate these species dynamics in Lake Patzcuaro, to the West of La Mintzita (Hall 2009). Experiments in La Mintzita showed that harvesting cattail decreases both the species’ dominance and abundance, allows light penetration, and increases plant and animal species diversity and richness (Hall et al. 2008).
Similarly, common reed (P. australis) has become a growing problem for North American wetlands because of its generalist behavior and efficient propagation. The invasion of common reed alters plant communities and hence, significantly changes soil properties (Uddin and Robinson 2017). According to Tulbure et al. (2007), common reed stands restrain water flow which affects water availability and quality, can form a thick and dense cover that is inappropriate for the native flora, and releases gallic acid, which is degraded by ultraviolet light to produce mesoxalic acid that attacks adults and seedlings of plants vulnerable to the toxin. Its large biomass—located well-above the soil surface—can turn a diverse ecosystem into a monospecific stand. Given this, common reed essentially outcompetes native plant species, decreasing the biodiversity of the areas it invades. Together with other disturbance factors, common reed communities can push many native species towards local extinction (Lindig Cisneros 2018).
Tall fescue (F. arundinacea) is an invasive species in North American grasslands and other native habitats. Tall fescue establishes in moist or altered areas, along roads, in eroded patches, and in moist depressions. Introduced tall fescue replaces native grassland over large extensions, with deleterious effects on biodiversity (Henson and Stafley 2009). The plant has allelopathic effects on many seeds and the accumulation of thick layers of its dead biomass—either due to natural or anthropogenic causes like mowing or grazing—hampers the germination of native plant seeds, deprives native seed-eating birds of food, and shades out native plants due to continued winter growth (Cheater 1992, Barnes et al. 1995, Henson and Stafley 2009, California Invasive Plant Council 2019).
In a first attempt to improve the conditions in the La Mintzita wetland, our project goals were to 1) describe the status of the vegetation in 2021 and compare it with the 2005–2015 community composition data reported by Rodríguez-Arias (2018); and 2) propose restoration strategies to policy makers and the local community focused on biocultural, productive, and ecocentric approaches to ecological restoration.
In general, we propose to control the dominant species by means of harvesting and eradication to decrease their dominance and increase the diversity of native plants. We focused on traditional harvesting of T. domingensis and use of P. australis for handicraft markets to provide a win-win project that offers local inhabitants economic incentives to restore the wetland. As harvesting of T. domingensis is an ancient cultural practice that can be reintroduced in La Mintzita, we propose a biocultural approach to restoration for areas dominated by this species. To increase biodiversity of the wetland with removal of P. australis for use as a building material and handicrafts, a productive restoration approach aims to increase productivity of the wetland system. Finally, tall fescue-dominated areas can be managed using an ecocentric approach.
Methods
Study Area
The La Mintzita spring is in the municipality of Morelia, Michoacán, Mexico, at an elevation of 1917 m a.s.l. (19°38′43″ N; 101°17′42″ W) (INEGI 1998). The climate in the region is subhumid with summer rainfall and a precipitation-temperature (P/T) ratio between 55 and 43.2. Winter rainfall represents less than 5% of the annual total. The thermal oscillation is low (13 to 34°C), and the temperature regime is of the Ganges-type (García 1988). The terrestrial vegetation surrounding the spring is mostly subtropical scrub. The aquatic vegetation includes submerged vegetation (Nymphaea mexicana, Stuckenia pectinata [syn Potamogeton pectinatus], and Ceratophyllum demersum), floating vegetation (Eichhornia crassipes [Rodríguez and Guevara 2000]), and emergent vegetation (dominated by T. domingensis and P. australis).
Sampling, Statistical, and Spatial Analysis
We sampled during the dry and rainy seasons of the year 2021. In the dry season, we resampled five perpendicular transects established in our previous studies (Escutia-Lara et al. 2009, Rodriguez-Arias et al. 2018). Each transect started at the border of the wetland vegetation and were separated from each other by 30 m. In each transect, six 1 m2 equidistant plots were marked. We recorded all species present in the plots and we evaluated their cover by presence or absence in 1 dm2 sub-plots. We collected voucher specimens for identification. This method was modified from the Great Lakes Environmental Indicators Project. It allows for standardization of methods and efficient sampling of this type of community and for comparison between sites (Frieswyk and Zedler 2006, Frieswyk and Zedler 2007, Frieswyk et al. 2007).
We identified plant species using Lot et al. (1998 and 1999), Villaseñor and Espinosa (1998), Lot (2000), Calderón de Rzedowski and Rzedowski (2001 and 2004) and Lot and Novelo (2004). The plants’ habitats were established using the Wetland Indicator Status in the United States Department of Agriculture Plants Database (USDA 2015). We identified obligate hydrophyte plants (code OBL), facultative wetland plants that are frequently found in wetlands, but also in non-wetlands (FACW), and facultative plants present in wetlands and non-wetlands (FAC). For this study, plants classified as facultative were corroborated to also occur outside the wetland. We compared our results with the data reported by Rodríguez-Arias et al. (2018), who followed the same sampling methodology. We compared species richness for the dry season data of the years 2005 and 2021 through rarefaction curves (sampling effort versus estimated species richness) and analyzed data in the software, Estimates 9.1.0 (Colwell 2013).
In the rainy season sampling, the transect-plot method was not applied because in our first visit during this season, Festuca arundinacea was even more dominant than during the dry season. Therefore we decided to make an exploration within each transect by recording every species found within a 1-m wide band centered in the transect with the goal of finding as many native species as possible. We are aware that by modifying the sampling method we covered more area in 2021 than in previous samplings, therefore increasing the chances of finding more species in 2021 than in 2005.
Due to the changes in species richness and in the spatial distribution of the dominant natives, as well as the increment in the area covered by the invasive species since the year 2015, we also analyzed aerial photographs which covered the entire wetland. The images were taken in six flights using a DJI drone (Mavic Mini, Shenzhen, China). The aerial photographs were processed in the application Agisoft Metashape to create an ortho-mosaic, which we analyzed using QGIS software v3.16. The generated GIS image was used to map plant cover types and grazed areas, and for establishing different zones for implementing restoration efforts. To establish cover types, an area was considered dominated by a single species if that species represented at least 80% of the canopy cover. The impact of cattle was evaluated by the effect of trampling and grazing in two categories: low intensity (areas with a canopy cover between 80 and 100% and at least 40 cm tall), and high intensity (areas with very short vegetation and exposed soil). We also mapped the density of permanent trails livestock make to move across the wetland.
Estimating Southern Cattail Potential Productivity
To estimate the potential productivity of cattail dominated areas and assess the feasibility of restoring plant diversity by reintroducing a cultural practice to the local inhabitants, leaves of southern cattail were harvested from six 1-m2 plots. The dry weight and length of the sampled leaves were measured and recorded, and the average number of leaves per square meter was calculated. The number of leaves needed for manufacturing T. domingensis bowls, boxes, and mats was estimated by measuring and weighing representative pieces, considering 20 cm of leaf left by craftsmen as remnant material during the manufacturing process (as observed by the authors during a workshop), from which data the wetland’s potential annual productivity under the proposed restoration plan was calculated. To know the criteria applied by craftsmen for collecting leaves and manufacturing of cattail pieces and to obtain a detailed understanding of the manufacturing process, both authors attended training courses for the creation of T. domingensis pieces, delivered by expert craftsmen from Pátzcuaro, Michoacán, in July and August 2021.
Results
Vegetation Characterization
The results from our 2021 dry season sample showed a lower species richness than that reported by Rodríguez-Arias et al. (2018) for the year 2005. Our estimation from rarefaction curves of the expected number of species for the dry season differed significantly between sampling years (Figure 1), the 2005 and 2021 curves displaying no overlapping in their confidence intervals. For 2005, species richness estimation was 22 ± 2.61 and for 2021 was 13 ± 1.54 species. Furthermore, tall fescue had between 60% and 100% cover in nine plots and seven of these were 100%, covering 28% of the combined area of the permanent plots in 2021.
Species richness rarefaction curves for the 2005 and 2021 dry seasons showing a significant difference between years. Sampling unit was permanent plots along five transects.
The decrease in species richness for the 2021 dry season and the substantial increase in cover of tall fescue in the permanent plots led us to modify the sampling method as already described. We found a total of 27 plant species, 15 of which were obligate wetland hydrophytes and six species were wetland facultatives. The number of species found in the plots every year from 2005 to 2015 varied (Figure 2) from a minimum of 19 (in 2010) to a maximum of 41 species (in 2015), decreasing to 27 in 2021 (Figure 2). It is important to note that the sampling effort in 2021 was higher than any other year, and it is possible that 27 species is close to the actual number of remaining species in the permanent sampled area of the wetland.
Observed changes in total, wetland obligate, and wetland facultative species richness in the rainy seasons of the years 2005 and 2021. Sampling units for the period 2005 to 2015 are permanent plots and for 2021 the sampling units was the area defined by each transect length and a 1 m wide band centered in each transect.
Spatial Analysis
Our analysis of the obtained ortho-mosaic of the wetland showed that T. domingensis, P. australis, and F. arundinacea were the dominant species as expected. We estimated the total extent of the remnant wetland to be 13.09 ha, of which 4.8 ha had no dominance by any species, 4.2 ha were dominated by southern cattail, 2.3 ha by common reed, and 1.75 ha by tall fescue that now covers 13.4% of the wetland area (Figure 3). The results of our spatial analysis, and field work, showed that grazing has been the only negative impact on the wetland in recent years. Fires had a severe impact in the period between 2005 and 2015, but no evidence of recent severe fires was observed during field trips. The number of heads of livestock (mostly cattle) grazing in the study area during the year 2021 was 60, which corresponds to 4.6 per ha. We observed an extensive area of vegetation negatively impacted by grazing. A 1.29 ha area with several cattle trails (1.8 km in length) suffered low-intensity grazing, as well as an 0.68 ha area heavily grazed (Figure 4).
Spatial distribution of the most abundant species in the La Mintzita wetland. Southern cattail (T. domingensis), common reed (P. australis), and tall fescue (F. arundinacea).
Areas impacted by low and high intensity grazing in the cover areas of the most abundant species. Southern cattail (T. domingensis), common reed (P. australis), and tall fescue (F. arundinacea).
Southern Cattail Potential Productivity
The results of the estimates of southern cattail average leaf dry weight, leaf length and number of useful leaves per square meter showed averages of 5.4 g per leaf, 201.4 cm leaf length, and 39 leaves/m2. Our estimation of remnant material calculated as unused leaf length is shown in Table 1.
Estimation of the potential productivity of handicraft units made from T. domingensis leaves in the La Mintzita per type of piece, hectare, and year. Except potential production data, all other values are means.
Table 1 also shows the results of our assessment of the potential productivity of T. domingensis leaves in the study area. Of the total extent of the wetland (13.09 ha), 3.64 ha are covered by usable T. domingensis, of which, based on traditional use in other wetlands in the region, 1.20 ha (33%) could be harvested to prevent negative impacts on native vegetation. Through monitoring and adaptive management this percentage can be modified in the future. Our results show that the La Mintzita wetland could potentially produce an annual supply of T. domingensis leaves sufficient for producing from 2,529 large pieces like chests to 61,622 small pieces like tortilla baskets (Table 1).
Proposed Environmental Restoration Regime
In the following paragraphs we justify our proposed strategy for environmental restoration of the La Mintzita spring wetland based on the mosaic of opportunities provided by the biocultural, productive, and ecocentric restoration approaches, each addressing one of the three dominant species in the wetland.
Biocultural Restoration Management of T. domingensis
Because it has been experimentally demonstrated in the Mintzita wetlands that T. domingensis harvest increases biodiversity, we propose that management of this species should follow a biocultural approach of environmental restoration to allow both the rehabilitation of the degraded landscape and the renewal and strengthening of the local cultural practices and identity, that in turn favors the resilience of the socio-ecological system. Hall et al. (2008), showed that after one year of T. domingensis removal, harvesting increased species richness at both the plot (14-m2) and wetland scales, increased the Shannon diversity index at the plot and subplot (1-m2) scales, and changed plant community composition (measured by Bray-Curtis distance) relative to control plots. Harvesting cattail decreases both the species’ dominance and abundance, allows light penetration, and increases plant and animal species diversity and richness (Hall et al. 2008, Lishawa et al. 2019, Lishawa et al. 2020). Harvesting T. domingensis live plants and leaf litter increases the phylogenetic diversity and species richness when compared to cutting and leaving the biomass in situ (Bansal et al. 2019).
The history of cattail gathering by local cultures in the wetlands of the Mexican Central Plateau region strongly supports applying the biocultural restoration approach for its management. Several peoples, including the Purhépecha (Reyes 1992) and Mexica (Heyden 1983), wove cattail leaves to create utensils and harvested the plant to use it as fertilizer and construction material for lacustrine agricultural systems (chinampas), and, since the Spanish conquest, as animal feed (West 1948, Heyden 1983, Albores Zárate 1995). In Michoacán, large areas of cattail are harvested and used for weaving handicrafts (Reyes 1992). Controlling T. domingensis in La Mintzita through harvest could provide a sustainable management strategy and an economic incentive for conservation of its biodiversity. Local inhabitants are interested in learning how to make handicrafts for sale. There is demand for Typha products both by permanent residents in the region and tourists, but no market or cost-opportunity studies have been made.
Productive Restoration Management of P. Australis
In our proposal for restoration of La Mintzita, the management of P. australis follows a productive restoration approach to prevent further expansion of this invasive by generating sustainable land management aimed at the provision of economic benefits for the local inhabitants (Ceccon 2013, Borda-Niño et al. 2016).
The productive management of common reed is justified by the economic potential of harvesting the plant to create handicrafts or to be used as a building material (Pude et al. 2005, Köbbing et al. 2013). Escutia-Lara et al. (2012) tested the effect of harvesting P. australis on the native species richness and species composition in the La Mintzita wetland. The main finding was that up to nine native species colonized plots where common reed was totally removed every two months. This study demonstrates that harvesting common reed can be an alternative to the use of herbicides—and the concomital negative environmental impact of this practice—providing an efficient management strategy to control, not eliminate, this plant in western Mexico, including the La Mintzita wetland (Escutia-Lara et al. 2012). Elimination of invasive species has proven elusive either for ecological reasons or economic limitations (Weidlich et al. 2019). We consider that establishing a sustainable use strategy for the species is a viable alternative.
Ecocentric Restoration Management of F. arundinacea
We propose managing F. arundinacea through an ecocentric restoration approach both because the benefits of its control would be mostly for the wetland itself, and because the community does not perceive any economic incentive coming from the species. Invasion of the La Mintzita wetland by F. arundinacea is of particular concern due to the displacement of all native species and the known problems for its control, even requiring the use of aggressive herbicides (Washburn and Barnes 2000). For restoring the area covered by F. arundinacea, we suggest that black plastic winter solarization might be effective. Marushia and Allen (2011) found that black plastic winter solarization outperformed the use of herbicides, mowing, and disking, and it increased the cover of native species in experimental plots presown with native species.
Zoning
We made a zoning proposal based on the above-described restoration strategies, historical reports, and the results of this study, which divides the study area into six zones (Figure 5), for each of which we defined the following restoration and management strategies.
Zoning proposed for environmental restoration of the La Mintzita wetland.
Lagoon and channel zone—The lagoon and channel areas require the control of the water lily (Eichhornia crassipes) and the submerged large-flowered waterweed (Egeria densa), control measures already undertaken by county and state environmental authorities.
Conservation zone—The conservation zone has an extension of 1.30 ha located parallel to the channel subzone with a 20 m width. The only activity allowed in this zone is the control-harvest of common reed (because it is an invasive) made exclusively outside the water birds nesting season.
Biocultural restoration zone (T. domingensis)—The biocultural restoration zone extends over 3.64 ha located between the limits of the conservation zone and the boundary of the T. domingensis distribution area away from the channel subzone. The approximate recommended maximum annual harvested area is 33% of the total for the zone.
Productive restoration zone (P. australis)—The productive restoration zone corresponds to the 2.3 ha of patches occupied by P. australis posing a threat to the wetland where management consist on removal as a material for different uses.
Ecocentric restoration zone (F. arundinacea)—Corresponds to seasonally flooded southern part of the wetland, where if the restoration of the soil hydric dynamics. Could be achieved by restoring channels that have been filled with sediment and allowing water from a channelized spring to flow again into the wetland where 1.75 ha of native wetland species could be incorporated.
Discussion
Our study showed the negative shift in the floristic composition trajectory in the La Mintzita wetland that has been occurring throughout almost two decades. The changes in floristic composition that Rodriguez-Arias et al. (2018) observed during the 2005–2015 period were already indicating a radical modification in composition of the plant community, which was corroborated by comparison of previous years’ results with our observations in 2021. Although the data on species richness is not conclusive, in particular for rainy seasons, the significant increase in cover of tall fescue is a major concern. Our findings demonstrate the urgency with which actions must be applied in the following years to revert the negative floristic composition trajectory.
Redirecting the floristic composition trajectory is required for maintaining the wetland and the ecosystem services it provides, including water quality improvement, which is of high priority because of its importance as the main water source for the urban population of Morelia. Our proposal of a multi-faceted restoration strategy incorporating several approaches will enhance future opportunities for the La Mintzita wetland and putting it into practice is essential for its prosperity in forthcoming years.
Rodríguez-Arias et al. (2018) previously demonstrated that the removal of livestock from the wetland was correlated with an increase in the abundance of the invasive species F. arundinacea; possibly because it was no longer consumed. As reported in Rodriguez-Arias et al. (2018), tall fescue registered a statistically significant increase in the permanent plots from 2.49% cover (year 2012) to 8.06% (2015) after cattle were removed. By 2021, tall fescue covered 28% of the permanent plots despite the fact that cattle were reintroduced by local farmers.
Clearly the interaction between cattle and tall fescue needs to be investigated at La Mintzita to establish the best restoration strategy, but livestock grazing must be ultimately banned in the wetland because of its potentially degrading effect through soil compaction, weed dispersal, trampling of the vegetation, and water contamination with animal wastes, which leads to weed infestation, a decrease in the abundance and diversity of the native flora, and poor water quality (Peters et al. 2015). Therefore, the simultaneous removal of tall fescue cover and livestock will prevent livestock from consuming native vegetation and prevent tall fescue from expanding.
Adequate management of fire is also of prime importance for the future of the wetland since induced fires caused major disturbances in the past. Between 2006 and 2012, five major fires occurred (Rodríguez-Arias et al. 2018) during one of which burned the peat soil in a large area of the wetland. Prescribed burning might be applied after assessing the best conditions for this practice. From observations of past fires, it seems that burnings must be made in the early morning hours in the early dry season (October to February) before arrival of the hottest days of this season (from March to May). Whenever possible, the use of fire should be avoided and practices like mowing and extraction of dry litter are preferred.
Because the deterioration of wetlands is frequently linked to alterations of the hydrological system, either directly or indirectly, appropriate measures must be taken to improve the hydrological regime of the watershed including the control of urban sprawl and the restoration of upland vegetation (Álvarez-Cobelas et al. 2001). However, addressing hydrological issues in this socio-ecological system is a highly complex task that will require a transdisciplinary approach.
Successful environmental management and restoration involves good design practices as well as well-funded execution. Conserving biodiversity and taking advantage of the opportunities for economic development is a shared-effort equation, in particular requiring the participation of the different sectors of society, governmental institutions, and the regulation currently in force (Delfín-Alfonso 2014). Municipal authorities have recently taken steps to begin biocultural restoration by harvesting cattail and sponsoring a workshop for local inhabitants to learn how to make handicrafts. Monitoring to asses the effects of harvesting on wetland species composition is under way. Under Mexican law, federal, state and municipal authorities can declare protected natural areas. La Mintzita is protected by both federal (as a RAMSAR wetland) and state law (because it was declared as a natural protected area by the State Government). Also, the water body is under the responsibility of a federal agency (CONAGUA). Finally, urban development in the water catchment is a municipal responsibility. This makes management difficult in La Mintzita because coordinating these federal, state, and municipal agencies is a very complex task. Our proposal of targeting different problems with different restoration approaches might facilitate actions by different government agencies. Biocultural restoration can be facilitated and carried out by state and municipal authorities, as well as productive management and ecocentric restoration by federal authorities.
In conclusion, the La Mintzita wetland has been impacted by multiple causes; however, recovery actions are technically feasible, but require working together with stakeholders, local inhabitants, the municipality, including the people of the city of Morelia, academia, and state and federal authorities to incorporate different approaches to restoration simultaneously. This approach might be useful in other wetland systems with a long history of human occupation worldwide.
Softshell turtle. Source: Goodrich, S.G. 1859. Animal Kingdom Illustrated Vol 2. (New York, NY: Derby & Jackson), The Florida Center for Instructional Technology, College of Education, University of South Florida, fcit.usf.edu.
Footnotes
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