Wetlands can be defined as the areas where amounts of water cover the soil or an ecosystem that is permanently or seasonally flooded by water. Although wetlands exist naturally and are sustainable ecosystems, they face the risk of destruction from human-made structures. Such human-made structures include levees, hydrological dams, tunnels, and drainage features such as bridges. The human-made structures have positive and negative impacts on wetlands. A meta-synthesis has been conducted on eight articles to identify the effect of human-made structures on wetlands, and the findings were recorded. The findings show that human-made structures cause more harm than good to wetlands. Therefore, we should not continue to allow development on wetlands.

Effects and Impacts of Human-made Structures have on Wetlands

Introduction

            Human-made structures are a consequence of developments, which have recently become a threat to wetlands worldwide. This is often a debatable point since each development is associated with some good. For instance, levees are usually constructed to prevent flooding near large water bodies. Bridges and railroads make transport more affordable and spare habitable land for other use like farming. However, sometimes the development of structures also poses risks to the wetland. For instance, the construction of levee systems has led to an increase in flood risks through levee breaches. This is the origin of a critical dilemma in urban development planning and policy drafting on whether authorities should allow developments in wetlands. In acknowledgment of the potential benefits and dangers of human-made structures on wetlands, this research aims to weigh the effects of such structres and take a stance on whether development should be allowed on wetlands.

Methodology

The guiding research question for this work is; should we continue to allow development on wetlands? As such, the researcher probes the impacts of human-made structures on wetlands by collecting data that can help in achieving the objective of the study, which is to understand the importance of keeping wetlands untouched, the importance of human-made structures and their positive and negative effects, and maybe finding a balance in between. Within the scope of this research, a wetland is defined as is an ecosystem that is permanently or seasonally flooded by water. Such ecosystems include swamps, marshes, bogs, and connected sub-ecosystems such rivers and dams. Also, human-made structures include bridges, flood walls, seawalls, harbor walls, tunnels, pontoons, railroads, and other structures that do not exist naturally near a wetland.

The researcher has adopted qualitative research methods, particularly meta synthesis. Meta synthesis is a type of systematic review where a researcher collects qualitative data to integrate and interpret patterns and come up with findings that can help develop a theory (Erwin et al., 2011). The researcher has collected data from peer review journal articles and grey literature which concerns the three objectives of the study. Also, the researcher relied on bibliographic data and key words to find the appropriate and relevant resources. The inclusion criteria were articles published since 2010 and must have keywords and phrases such as wetlands, roads, the impact of human-made structures on wetlands, causes of floods, loos of wetlands, and human activities on wetlands.

Preliminary search found more than 30 articles both peer review and web pages. The researcher had to narrow down to the most relevant ones by judging their validity based on the publisher’s background information and relevance of the article to the research. The researcher biased and favored articles published by natural science writers, published in credible websites such as those with domain extensions .org, .gov, and .int, .com and those published in journals of natural science. In the end, the researcher resolved to include seven peer-review journals in the meta synthesis.

Data Collection and Analysis

The researcher read all the eight articles and extracted the relevant data regarding the type of human-made structure, the type of wetland, the location of the wetland, impacts of the human-made structures to the wetland in its surrounding, current and proposed solutions, and the history of the impact. The data was coded in verbatim on a table, which would help the researcher organize it and further extrapolate relevant themes. The researcher conducted a narrative synthesis which reveals the themes regarding the importance of keeping wetlands untouched, the importance of human-made structures and their positive and negative effects, and maybe finding a balance in between. The researcher is careful to identify and avoid the potential effects of modifiers unrelated to human-made structures such as natural earth processes.

Findings and Discussion

The majority of human-made structures cause multiple hydraulic constrictions on wetlands. An example of hydraulic constrictions can be identified using the Missouri River Floodway model (Dierauer et al., 2012). Flood risks are associated with high-velocity rates caused by multiple hydraulic constrictions in wetlands (Dierauer et al., 2012). Sekomo et al. (2010) add that the high flood risk is due to erosion exposure. In addition, erosion can also tamper with the stream geometry by damaging the silt and clay blanket after a hydraulic constriction. When there are multiple hydraulic constrictions, the blanket is susceptible to damage at the constriction point. Through increased velocities, levees can cause an increase in water surface elevations (Sekomo et al., 2010). Such an increase can be a problem in some critical reaches as large amounts of energy are required to push water in the constricted locations. Effects of levee also result in economic interferences – for instance, when a flood occurs, there are expenditures incurred in flood fights and habitat restoration (Dierauer et al., 2012). Hence, a major challenge posed by human-made constructions is hydrostatic constriction.

            Hydroelectric dams tamper with the river’s hydrology and the concentration and amount of nutrients in wetlands. When the concentration and amount of nutrients are altered, the species that survive in wetlands are also directly affected (Ezcurra et al., 2019). Some wetlands have freshwater, which some species survive in, and thus their lifecycle may change when the waters are altered. Hydroelectric dams can lead to high water salinity as downstream water pulses reduce (Ezcurra et al., 2019). In the aftermath, the groundwater table can lower, making water unsafe for drinking and irrigation activities in wetlands locations (Ezcurra et al., 2019; Sekomo et al., 2010). Decomposed organic matter drowned in the dam reservoir can hinder, leading to leaching from the flooded minerals. The normalcy of a wetland can also be affected by the dam’s reservoir, which might trap essential sediments vital in the natural cycle of wetlands (Ezcurra et al., 2019). When water is released downstream, the water comes with unnaturally high energy that carries few sediments. Such reduction in sediment leads to lower production in the coastline of coastal wetlands. Riverbeds are also eroded when the concentration of sediments is reduced. As a result, the riverbed is deepened, unlike the surrounding water table (Yang et al., 2018). This causes the groundwater to become surface water as the water rushes into the channel or river. Also, dams disrupt the flow and composition of water in channels and rivers (Ezcurra et al., 2019). The greenhouse gases released by dams also destroy carbon sinks found in wetlands. Generally, hydrological changes caused by dams have contributed to the damage of wetlands.

Tunnels affect wetland locations in different ways. During tunnel construction, the tunnel operations lead to exposal of excavated materials used which might ruin wetlands (Gong et al., 2018). Washing operations that happen during tunnel constructions cause stream sedimentation. Large volumes of excavated rock can affect wetlands if not filled incorrectly. Chemical contamination from large amounts of cement plants is inevitable and thus destroys wetlands during tunnel operations (Liu et al., 2015). The construction plant of tunnels is also harmful to wetlands as it can destroy the habitat of species that survive in wetlands.  In general, the local ground environment is affected by tunnels during tunnel construction (Liu et al., 2015). Groundwater recharge can occur as a result of infiltration of precipitation that happens in outcropping carbonate rocks.

            Other pathways such as bridges are also a challenge to natural existence of wetlands. When bridges are constructed on flood plains or in adjacent river bluffs, it is more likely that erosion, sedimentation, and stream turbidity will occur. The number of roads with a catchment also affects wetlands’ hydrological responses (McCauley et al., 2015). This is because the catchment can form barriers to flow. It is inevitable for devegatation to take place in wetlands that have undergone bridge construction. Vehicle traffic on the constructed bridges or other drainage features is a problem in maintaining wetlands’ quality (McCauley et al., 2015). Mostly, the water becomes polluted by the asbestos fibers and the hydrocarbons from the sediments of heavy metals.

Canals have also contributed to destroying wetlands. Human-made canals are responsible for interrupting tidal inundations, which are necessary for maintaining ecosystems in coastline wetlands—water level changes due to interruption of the natural flow of tidal inundations (Kirwan & Megonigal, 2013). For instance, oil and gas explorations during the digging of canals in Lake Maurepas led to a need for larger boats as the channels deepened and widened. As a result, the channels failed to meander as they were dug deep. Channel failure destroyed vegetation responsible for stabilizing the bank structure. Additionally, there resulted in a barrier to the natural flow of water across the wetlands. Lack of a natural flow of water led to flooding in the wetland locations.

            Human-made structures do not entirely bring negative impacts. For instance, despite levees having negative impacts on wetlands, they ensure subsurface flow necessary for contaminant removal in wetlands (Dierauer et al., 2012). The horizontal levee is vital where some wetlands are built between the coastal levee and tidal marshes. It also protects other existing levees from erosion and coastal flooding caused by storm waves. Hydrology plays an essential role in contaminant removal in wetlands (Ezcurra et al., 2019). Sometimes, levees alter with the hydrological cycle to prevent overbank flooding that happens mostly seasonally. By preventing overbank flooding, soils can acquire the needed nutrients (Dierauer et al., 2012). Additionally, there is a high chance of flood plains and the river acquiring nutrients through flood pulses.

Synthesis

            Given the research findings and discussion, there are more harms of artificial structures to wetlands than good. Therefore, we should not continue to allow development on wetlands. According to Dierauer et al. (2012) and Sekomo et al. (2010), human-made structures cause hydraulic constrictions associated with high flood risk, erosion, and alteration to the ecological patterns of wetlands. Ezcurra et al. (2019) and Sekomo et al. (2010) explain that hydroelectric dams change the ecosystem of a wetland by tampering with salinity and are a threat to global temperature. According to Gong et al. (2018) and Liu et al. (2015) construction of tunnels leads to contamination of water in the wetland and general change in the life cycle at the wetland. This is supported by McCauley et al. (2015), who also adds that bridges weaken catchment barriers, cause erosion, sedimentation, and stream turbidity. Besides, Kirwan & Megonigal (2013) have found that canals destroy wetlands and are a barrier to the natural flow of water across the wetlands. Nevertheless, Dierauer et al. (2012) explain that some structures ensure subsurface flow necessary for wetland contaminant removal, which is good for a wetland.

Conclusion

According to the research, the development of wetlands should not be allowed. Human activities happening in wetlands are destroying wetlands at an alarming rate. The more developments are allowed in wetlands, the more the chances of complete damage to wetlands. While the developments in wetlands usually come from good economic intentions, the structures might fail to deliver the intended course and harm wetlands. From levees, bridges, to tunnels, it is evident that the positive impacts are less than the negative impacts. With that in mind, it will be inevitable to harm wetlands when the development of wetlands is allowed.