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Restoring Aquatic Ecosystems



Plants, animals, other organisms, even the weather and the landscape itself form a bubble of life that is defined by the sum characteristics of each individual member referred to as an ‘Ecosystem’. They possess biotic or living parts, as well as abiotic or non-living parts. Living parts include plants, animals, and microorganisms as well. The nonliving components include the physical space, geology, climate, and more. Unfortunately, a lot of ecosystems around the world are under threat due to modernization. Species are disappearing causing trophic cascades. Global warming is causing extreme alterations in the environment which are straining established food web dynamics. Seeing the deep and complex interconnectedness of each species, it’s not difficult to realize that protecting ecosystems is beneficial for humans. That is why we should strive to protect and restore ecosystems.


Ecosystem restoration

A lot of our ecosystems are damaged. However, through ecosystem restoration, there is a chance to save each damaged ecosystem and restore them to their original state. Healthier ecosystems and richer biodiversity are beneficial to humans because they lead to bigger yields in agriculture.


There are a wide variety of ecosystem restoration methods available like planting trees, removing environmental pressures, and helping nature recover on its own. Although it is highly preferable that an ecosystem is returned to its original state, it is not always possible or practical. For example, we can’t simply destroy property just to return them back to its original state because it will leave some people without a home. We couldn’t revert farmlands to forests as well, a farmer would lose a source of income and food production would be reduced. As much as possible, restoration should return ecosystems to their original state. However, it should be balanced with practicality.


Restoring ecosystems has a huge positive impact on many aspects of our life in the long run. It can be thought of as a long-term investment. Researchers have projected that the restoration of 350 million hectares of damaged aquatic and terrestrial ecosystems could potentially lead to income generation of up to 9 trillion US dollars in ecosystem services. Moreover, restoring ecosystems could exert a positive impact on our greenhouse gas problem. Ecosystem restoration may lead to the removal of up to 13 to 26 gigatons of greenhouse gases from the atmosphere. Estimates show that the economic benefits that ecosystem restoration brings, is nine times greater than its investment cost. Doing nothing can lead to environmental damage which could ultimately lead to economic damage which could cost three times more than ecosystem restoration.


Any kind of ecosystem be it terrestrial, like forests, farmlands, and cities, or aquatic, like oceans, lakes, and wetlands, can be restored. However, a restoration method that is effective in one ecosystem may not be applicable to another. Nowadays, people are empowered to launch campaigns aimed at restoring ecosystems. Besides government and developmental agencies, businesses, communities, or even a single individual can launch their restoration initiatives.


Why should we Restore our Ecosystems?

There is a multitude of reasons why ecosystems need to be restored. These reasons can be grouped into five rationales, which include technocratic, biotic, heuristic, idealistic, and pragmatic.


Government agencies and or other large organizations may conduct ecosystem restoration projects to satisfy specific mandates, this is the technocratic rationale.


When the reason for ecosystem restoration is for the sake of local biodiversity, then this rationale is classified as biotic.


To get a better understanding of ecological principles and biotic expressions it is useful to conduct ecosystem restoration activities, this rationale is classified as heuristic.


When a person is driven by personal and cultural expression of concern or atonement for environmental degradation, re-engagement with nature, and or spiritual fulfilment with regards to restoring our ecosystems, then that person has an idealistic rationale for their cause.


Ecosystems provide a wide range of natural services and products, realizing this and restoring them for the purpose of getting these natural services and products is the pragmatic rationale for restoring ecosystems.


The technocratic rationale of restoration in its current state is too narrow in scope. Mandates of government agencies and or large organizations should entertain the pragmatic rationale. In other words, they should view ecosystem restoration as an opportunity to improve the country with regard to resources. Aside from that, it would be highly beneficial if the idealistic rationale is instilled into the minds of those who are in the position of power in government agencies and or large organizations. This will serve as a strong driving force for the government agencies and or large organizations to push through with their ecosystem restoration projects and see to it that it succeeds.


Aquatic Restoration

There are several factors that lead to the degradation of a lot of aquatic ecosystems around the globe. The nature of our anthropogenic activities and the growing population are the primary driving factors to the degradation of these ecosystems. Negative changes such as loss of biodiversity, chemical pollution leading to excess nutrients and contaminants in the aquatic environment, a sharp decline in apex predator populations and ecosystem engineers, and homogenization of biological communities. Recalling the pragmatic rationale for restoring the ecosystem, there is a clearly defined need of reversing the decline in aquatic biodiversity so that the natural services and products that are derived from them won’t be compromised.


The differences between freshwater and marine ecosystems is a huge factor when it comes to aquatic restoration.

  • Freshwater environments tend to be smaller which exerts a greater spatial restriction on the organisms that inhabit there.

  • Freshwater ecosystems include rooted vegetation and insects which exerts a unique influence on the environment.

  • Organisms living in marine ecosystems are better dispersed and have better connectivity with each other.

These differences should be taken into account when trying to use conservation methodologies designed for freshwater ecosystems on marine ecosystems.



Rivers and Lakes

Rivers, lakes, and all sorts of freshwater ecosystems have been a source of food, water, and even energy for a huge number of people. Moreover, they provide protection from both droughts and floods. They provide a home for many plants and animals. That is why we should value our freshwater ecosystems by doing the following:


Clean up

Whatever junk is dumped or washed off through runoff should be removed from the body of water. This way, the water quality and aesthetics would improve. People can appreciate the water body better when it is aesthetically pleasing and would be motivated to protect it.


Control access

There should be well-defined but easy-to-use access points for humans, animals, and even machinery. These access points should be situated in such a way that considers the behaviour of animals. For example, if an area is a known fish spawning ground, humans and boats or any kind of machinery should not be allowed to enter that area to avoid disturbing the fragile lifecycle of the fishes. This does not mean that humans should no longer be allowed to enjoy the body of water. Most of the time, there would be areas where human activity would have minimal impact.


Restore vegetation

It is well known that vegetation near a body of water offers benefits to that body of water. Thus, thinned-out vegetation along the banks of rivers and lakes should be restored by planting indigenous species. By doing so, with the restoration of the indigenous plant species a buffer zone between the water and nearby source of pollution is created. Restoration of vegetation should also include the removal of invasive alien species.


Plan with sustainability in mind

Fishing and harvesting should be done in such a way that doesn’t deplete fish populations. This should be done on other resources as well. Check the water for sources of pollution like sewage, chemical pollutants, industrial wastes, and other kinds of effluents. Agencies that are concerned with restoring ecosystems should make agreements or pay incentives to encourage reductions in agricultural chemicals.


Current Situation

Many developed countries have made significant progress in reducing organic waste, nutrients, and contaminants that enter freshwater ecosystems. While older generations of sewage treatment plants introduced large amounts of organic pollution, increased biological oxygen demand, and lowered oxygen levels in bodies of water, newer ones have addressed this issue and found a way to minimize these problems. Phosphate levels in most water bodies have also lessened in most developed countries. This can be attributed to the removal of phosphate as an ingredient in laundry detergents, the improvement of sewage collection, and the implementation of tertiary treatment that effectively removes phosphate. Acidification of water bodies that contains little to no lime is also reduced. The acidification problem was resolved by using source-related filtering technologies and reducing sulphur in fuel. Moreover, active restoration efforts are made to restore damaged freshwater bodies. Still, high nitrate levels continue to be a problem even in these industrialized countries. Moreover, developing countries all over the world are still struggling to control the amount of nutrients that are entering their bodies of water leading to eutrophication.


Deficits in the Restoration Efforts

Although restoration efforts have increased, most of them fail to follow a systematic and evidence-based approach. There are little to no verifiable evaluations of the efficacy of these restoration projects and whether the legally mandated goals have been achieved. Restoration methods that are based on well-accepted theory and are aimed at regaining the hydrogeomorphic, biogeochemical and ecological processes that make up a healthy river do exist. However, the problem is with the implementation and assessment of these methods, they need to be studied further. This was made evident by a case study that was conducted in Europe. In this study, gravel introduction and excavator-based substrate loosening showed short-term positive effects, about a year or less. Regrettably, these methods had long-term negative effects not on the area where the restoration methods were used but downstream. Worse still, the scale of the negative effects overshadowed the short-term positive effects of gravel introduction and excavator-based substrate loosening.


There is a dire need for evidence-based assessment methodologies for the evaluation of restoration procedures. Aside from that, the taxonomic and spatial representativeness of different groups of species within an aquatic ecosystem should be taken into account as they may demonstrate varying responses to both ecosystem disturbances and restoration.


Challenges to restoration

Restoring ecosystems to a more favourable condition is already challenging in itself, how much more for restoring them to their original state. Here are some of the things that could make ecosystem restoration difficult:


Siltation and Colmation

Siltation and colmation of stream beds, especially when they occur in headwater areas, pose a serious threat to restoration efforts. Both siltation and colmation can make it challenging for endangered species of freshwater mussels and gravel spawning fishes to survive and develop. This problem is further exacerbated when water temperatures rise which can be brought about by thermal pollution. Siltation and colmation usually arise from catchment-dependent land use and in-stream modifications. With that said, catchment-scale should be considered when determining the proper in-stream measures to use.


Naturally Fragmented Ecosystem

Most critically endangered freshwater species live in stream ecosystems. The negative changes to structural habitat quality brought about by intense modification of stream courses and their catchments are the foremost challenges when it comes to restoration. Freshwater ecosystems are naturally more fragmented compared to marine ecosystems. This makes establishing connectivity within freshwater ecosystems problematic.


On the other hand, establishing connectivity is not always ideal, especially between naturally isolated systems. By doing so, homogenization of biological communities is likely to occur. As well as reduced resilience to environmental stressors. This happened in Europe’s dense system of man-made canals. The canals established connectivity in naturally isolated systems which lead to the dispersal of non-native species like the zebra mussels and Ponto-Caspian gobies. This dispersal of non-native species is threatening indigenous species.


In essence, the fragmented nature of freshwater ecosystems complicates the entire process of ecosystem restoration. It is not apparent which is better, to establish connectivity within a fragmented ecosystem or not.


Knowing the Ideal Restoration Target

This question can complicate the decision-making and planning processes of ecosystem restoration; “what is the ideal restoration target?” Is it enough if we improve the condition of some areas of water bodies and leave other areas in their current deteriorated state? Is it practical to improve the condition of the entire water body?


A case study that involved highly modified river systems in Germany offered insights regarding the complexity of setting an ideal restoration target. In this study, researchers introduced four different in-stream structures namely bank ripp-rapp, benched bank ripp-rapp, successively grown riparian wood and artificial deadwood to the river systems. The introduction of artificial deadwood was particularly effective in improving the common species population. However, the introduction of these in-stream structures was not able to restore the population of specialized endangered fishes. So would it be better to continue with this method of restoration, focusing on the common species population as the ideal restoration target? Or would it be better to employ other restoration methods and focus on the specialized endangered fishes as the ideal restoration target?


The complexity of structural habitat diversity restoration

Structural habitat diversity restoration is a key target in the restoration of streams and rivers. However, the restoration of structural habitat diversity is easier said than done. Although there are well-researched methods of achieving this kind of restoration, they aren’t free from problems. These problems include inadequacies in monitoring, insufficient taxonomic representation, and underrepresentation of negative results. Such problems can lead to unsatisfactory restoration decisions and practices.


Incomplete knowledge of the autecological requirements of certain species

A single species is bound to interact with the living and nonliving components of an ecosystem. How these interactions would play out is the main concern of autecology. Unfortunately, there is a huge deficit concerning the autecology of a wide range of species. This gap in knowledge is brought about by a lack of interest in these species. Making good restoration decisions without a good grasp of how every species within an ecosystem interact with its living and nonliving components would prove to be a complicated undertaking. To demonstrate just how important autecology is, even related species with similar life cycles and appearances may have disparate habitat requirements. To assume otherwise because of their close resemblance to each other may benefit one species but do harm to the other. Due to the fact that species pools can differ depending on the geographical region, restoration projects that may prove to be successful in one area may not be applicable in another.


Unknown causes of biodiversity decline

Restoring ecosystems is a troubleshooting process that involves determining the underlying cause of the problem. However, determining the underlying cause of the problem can be challenging. Sometimes, the cause of biodiversity decline is unknown, or there can be several environmental pressures that some of environmental pressures would be masked. Moreover, environmental pressures can interact with each other which makes them even more difficult to resolve.


The main environmental pressures that affect freshwater biodiversity negatively are well documented. However, the interactions between these environmental pressures are not well understood. Furthermore, it is also hard to deduce which environmental pressure is relatively more damaging and would need immediate action. Not all environmental pressures are well documented. There are other environmental pressures that, owing to their low impact, are not well understood. Despite having a low impact on ecosystems they are still able to complicate ecosystem restoration efforts. There is also the matter of emerging contaminants, since they are emerging there are a lot of things about them that aren’t known yet. This lack of or incomplete information can introduce uncertainties into the restoration efforts which may render them ineffective.



Oceans and Coasts

70 percent of the Earth’s surface is oceans and seas. These marine habitats are capable of generating 50 to 80 percent of the Earth’s oxygen. They also generate marine food products like fishes, seaweeds, and other kinds of seafood. Moreover, they can serve as a tourist attraction which makes them an important economic resource.


Active restoration approaches in the context of open marine and coastal systems can only be applied in ecosystems where the biogenic structure has been lost. Open marine and coastal systems include semi-terrestrial saltmarsh and mangrove vegetation, intertidal and subtidal seagrass beds, kelp beds, mollusc and polychaete reefs, and coral reefs. Species capable of biogenic structuring act as ‘ecosystem engineers’ because part of their natural behaviour involves modifying their environment to create new habitats or modifying the existing ones to suit their needs. Restoring species that act as ecosystem engineers leads to improvements in habitat structures which also influences ecosystem functioning and services.


Primary producers

Another important thing to note is the primary producers which are higher plants such as seagrasses, and seaweeds. These are usually found in salt marshes and corals and they provide primary production that is directly consumed by grazers.


Planting higher plants such as saltmarsh and mangrove species, and seagrasses is a technique that is often used in terrestrial and freshwater bank habitat restoration. This technique tends to be effective. In fact, studies have shown that planting seagrasses in clumps can improve survival. However, there are concerns that this technique may produce vegetation that lacks genetic diversity.


Reef-building species

Bivalve molluscs, serpulid worms, or corals are reef-building species. Their ability to settle in an area is enhanced by the use of artificial substrata, especially when they reproduce by mating with a nearby barnacle. With their enhanced ability to settle they can easily act as a replacement of biogenic structure which could lead to habitat restoration and resumption of ecosystem processes.


Semi-enclosed marine and coastal water bodies

There are several ways for restoring semi-enclosed marine and coastal water bodies. Restoring hydrological processes like the exchange between lagoons and the open sea or estuary is one way and is a good start. Something as simple as changing the rate at which sediments would be transported through a reservoir can be a step towards restoration. This approach has been used in managing coastal areas that have been realigned without using dykes or seawalls. There is one major drawback with this approach, which is it can take a while before erosional and drainage processes would resume. By realigning coastal areas closer to land, saline water would be brought in, killing terrestrial vegetation within the new coastal area. With the death of the terrestrial vegetation, saltmarsh plants can take over resulting in the formation of mudflats. Marshes created through this method would also take some time before their species composition, community structure, ecosystem functioning, and services would match natural marshes. Oftentimes, it may take decades before ecosystem services would resume. This method can be hastened by introducing spatial heterogeneity and some targeted restoration approaches. Managed re-alignment plus changing the rate at which sediments would be transported through a reservoir are two restoration methods that when combined can effectively restore semi-enclosed marine and coastal water bodies. However, it may take some time before full restoration is achieved.


Restoring ecosystems in disused docks

When macro-tidal ports are no longer used for commercial shipping they could create an artificial degraded ecosystem that is enclosed. Techniques used on lakes or reservoir management when used on deeper dock basins proved to be successful.


In docks that have high salinity, the presence of filter feeders such as mussels can aid in improving water quality through biofiltration. The mussels can be assisted with a mixing airlift pump so that biofiltration occurs at a higher rate. With the aid of the airlift pump, the total volume of the dock passed through every mussel within 1 to 2 days. The increase in biofiltration led to significant improvements in water clarity. The presence of the mussels also led to the removal of human pathogens from the water. On top of this, oxygen levels also increased. Furthermore, the change in temperature brought about by summer didn’t affect these improved oxygen levels. These improvements in the marine habitat led to the appearance of a thriving marine assemblage.


Special ecosystems would arise from disused docks. However, these ecosystems are fragile and tend to degrade easily. Restoring these ecosystems leads to the creation of artificial cubist marine lagoons within the big cities.


Open systems

Due to the large scale of open systems, removal of acute pollution sources or cessation of chronic impacts would lead to a relatively faster recovery. This is due to the fact that propagule and larval supply from unaffected areas can replenish the damaged ecosystems in the area that is beginning to recover.


For instance, in areas which was once tow fished or was once dredged for scallops, they seem to recover rapidly once the damaging activities have ceased. As a real world example, scallop dredging operations was ceased in an area off the Isle of Man to allow the scallop populations to replenish on its own. To everyone’s surprise, the scallop population recovered naturally faster than was expected. Moreover, the overall nature of the benthos became more heterogeneous. In other words, their biodiversity improved.


Rocky shore systems

Rocky shore systems can recover quickly from oil spills as long damaging clean-up methods are not used. One instance where clean-up methods turned out to be more damaging than the oil spill itself occurred in Torrey Canyon southwest Britain. The first generation dispersants that were used for the clean-up turned out to be more damaging than the oil itself. Using dispersants although effective, is not necessary. In fact, on shores that were left untreated because of seal populations recovery happened within 2 years. On the contrary, in areas where dispersants were used excessively, several species living in the area were killed. This includes keystone species which led to a decline in biodiversity. However, after the dispersants were removed ephemeral and fucoid algae proliferated which led to the return of limpets. The effects of the oil spill and the cleanup methods have a complex long-term effect on the marine ecosystem. Seaweeds became dense when the oil spill cleared but was quickly eaten up by the flourishing fauna. This led to several die offs which happened in some places and then led to a second flush of algae. Due to the complexity of the issue, it took around 10 years for the shores to recover completely. This goes to show that in wave-swept rocky substrates, letting natural re-colonization processes take place is the best option. However, this natural re-colonization processes should be facilitated by removing the source of the environmental pressure. Oil dispersants have now fallen out of favour due to their toxicity. Oil spills are now handled through manual clean-up and natural recovery processes.


Designation of effective marine protected areas

Designation of effective marine protected areas can remove extractive pressures and human disturbance from a specific habitat. This should be done with appropriate management regimes to minimize human disturbance and to allow marine ecosystems to recover naturally. When and where marine protected areas have been designated effectively, the effect on the area’s ecosystem is overwhelmingly positive. Successful implementation benefits not only fish populations but as well as invertebrate populations as well. One major drawback of marine protected areas is that the coverage of their positive effects is small. Another drawback is enforcement. Some marine protected areas are only marine protected areas by name only, protection isn’t strictly implemented. This is not ideal because the effectiveness of marine protected areas is highly dependent on how well the area is protected.



Artificially created habitats

Some freshwater and marine habitats are not natural but instead are man-made or artificial, if not artificially made they are highly modified. Some rivers have been deepened, straightened, or both for the purpose of navigation, canals, and irrigation. There are ponds and reservoirs that people created as a source of water for both people and livestock. Estuaries have been dredged and straightened to aid in navigation. Jetties, wharves, breakwaters, and enclosed dock basins were also created along coastal areas to aid in maritime activities. Channelization and canalization of rivers and the creation of hard coastal defences to aid against flooding could also create a unique habitat. Several offshore structures like oil rigs and wind farms can act as artificial reef habitats. Shipwrecks also provide shelter for several aquatic species that deliberately sinking old ships is now a recognized method for creating artificial reefs. For the past 50 years various methods of creating artificial reefs have been utilized to improve marine ecosystems, support diving tourism, recreational angling, and commercial fishing. It is entirely possible to create artificial habitats for the purpose of enhancing biodiversity.


Structural complexity of artificial habitats can lead to the formation of microhabitats including crevices and rock-pools. These can mitigate harsh tide-out conditions and boost biodiversity. Aside from that, they can increase the population of overexploited or threatened species.


Valuing our Marine Ecosystems

Something as important as oceans and coasts should be valued by doing the following:


Clean up

Gather and remove wastes present in the beaches and shores. Aside from that, clean-up involves reducing the usage of waste-generating items or recycling whatever waste is left behind. Essentially, by reducing the amount of waste that ends up in landfills, the amount of waste that ends up in our oceans are also reduced. Another thing that people should be wary of are products that contain microbeads and or microplastics. Using these products leads to the introduction of microbeads and microplastics into the sea and oceans which can harm marine life.


Restore vegetation above and below marine habitats

With regards to biodiversity, coastal ecosystems like salt marshes, mangroves, coral reefs, and sea-grass meadows are just as important as pelagic or open ocean habitats. They serve as an important shelter for juvenile and small fish species. Without these shelters, the population of the fish species that rely on them may decrease significantly.


Use the ocean wisely.

Coastal and ocean development and fishing are activities that can have a negative impact on marine ecosystems if they are done without thinking about sustainability. With that said, if the goal is sustainability, communities, authorities, and other stakeholders must be brought together to take action. For instance, groups can initiate sustainability projects such as creating and maintaining protected areas. Fishing communities could also come together under the guidance of a resource person to determine which areas to fish and which areas to protect.



Source:

https://www.genevaenvironmentnetwork.org/world-environment-day/

https://onlinelibrary.wiley.com/doi/10.1002/aqc.2702

https://conbio.onlinelibrary.wiley.com/doi/abs/10.1111/j.1523-1739.2006.00340.x


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