Ocean Acidification Under the DPSIR Model of Analysis: From Drivers to Change

Globally, there is nothing that shapes our lives more than the ocean. It covers the majority of surface area on Earth, with millions of people dependant on it as a resource. Above all, it has the ability to act as a carbon sink. However, due to rising levels of carbon dioxide emissions, the future of the world's oceans have become compromised significantly. Historically, this is able to be attributed to the Industrial Revolution, “when people first started burning fossil fuels, carbon dioxide concentrations in the atmosphere have risen from about 280 parts per million to 387 parts per million, a 39 percent increase” (EarthObservatory.nasa.gov). With rising carbon dioxide levels, the oceans absorb this and as a result their pH levels are lowered. Consequently, this has come to be known as ocean acidification (OA). OA has become an increasingly pervasive issue over the past few decades as emissions have steadily risen. In examining the terminology regarding OA, it is important to understand what that means, as Carol Turley states, “it should be noted that ocean pH is unlikely to become acidic (that is become lower than pH 7), and the term acidification reflects the process of becoming more acidic, just like warming reflects the process of increased temperature, although this could be from cold to not quite so cold” (Turley 16). A useful model of analysis to comprehend all aspects of the OA issue is the Driver-Pressure-State-Impact -Response model, more commonly referred to by its acronym DPSIR. This model aims to consolidate all aspects of societal and environmental responses. Through using the DPSIR model, I will investigate the how global history has led to the present state of OA and thus, how it should be responded to in order to maximize the mitigation efforts that are plausible. OA fits into the DPSIR model because it is anthropogenic emissions and activities which has driven it to its current position. It is also interesting because the acidification of marine waters is also responsible for numerous other issues within the ocean ecosystem. There are numerous effective ways of measuring this degradation but quantifying the extent that it will have on shaping the future of marine ecosystems is difficult to determine the scope of. Then, I will examine what the global policy response to this issue has been and the pressure for systemic change to occur.
Using the DPSIR model to guide the analysis for the exploration of the causes of OA there are numerous which can be found, however, “for the past 200 years, the rapid increase in anthropogenic atmospheric CO2, which directly leads to decreasing ocean pH through air–sea gas exchange, has been and continues to be caused by the burning of fossil fuels, deforestation, industrialization, cement production, and other land-use changes” (Guinotte and Fabry 320). Thus, these drivers are able to be classified into the more main categories of industry, economic reasons and technology use as they have become increasingly responsible for OA. As previously mentioned, there is a well-established link between the Industrial Revolution and the exponential rise of anthropogenic emissions (ACS.org). Furthermore, industry use has been one of the largest drivers of OA as it has been significantly involved in the release of carbon dioxide. These emissions from industrial uses have only two places to go, in the ocean which is able to uptake carbon dioxide from the atmosphere and the atmosphere itself:
Because CO2 is fairly soluble, a considerable portion of the emissions from fossil fuels must have moved from the atmosphere into the ocean...Observations of CO2 accumulation in the atmosphere and ocean show that they are approximately equal to the total amount emitted by burning of fossil fuels since 1850 (Tans 26-27)

Next, there are numerous economic drivers which are to blame as well, these include the need for profit as well as the need for production and consumption throughout various sectors like agriculture and transportation, among others. Economic drivers encompass numerous aspects and all impact ocean acidity. The need for humans to have their basic needs met, such as food, shelter, water and transportation all come at a cost. Economically, these must be met and businesses aim for the lowest price possible to potential consumers, consequently this usually comes at the cost of environmental degradation, with land pollutants impacting the sea. With population, the need for resources increase as well, in Canada alone, “ten percent of Canada's greenhouse gas emissions are from crop and livestock production” (AGR.gc.ca). If this trend is realized globally, the understanding becomes clear that there are numerous and far-reaching drivers contributing to anthropogenic emissions and in turn, to OA.

Drivers within the DPSIR analytical model give way to so-called pressures which are understood to be as what is able to be directly or indirectly responsible for. The most significant of these pressures is the emissions they are responsible for. The effects of emissions on OA is far reaching, but a “decrease in the pH of surface waters by 0.1 pH units and a reduced availability of free carbonate ions (CO32-) used by many marine invertebrates as part of the calcification process” (Kelly and Hoffman 980), are among the most damaging. Fossil fuel combustion and its release of carbon dioxide has been by far the most significant type of industrial waste harm. This pressure is able to be understood best when focused specifically on calcifying organisms, like coral reefs, as they receive the brunt of the impact. Global emissions specifically are causing “decreasing seawater carbonate ion (C032_) concentrations because of rising atmospheric CO2 predicted to lower rates of calcium carbonate (CaCO3) production by corals such that, within decades, rates of reef erosion will exceed rates of reef accretion across much of the tropics and sub-tropics” (Pandolfi 418). Further, it is coral reefs which are key to the survival and ability for many marine species to thrive. It is the pressure of emissions which have been driven by industrial, technology and economic reasons, which collectively has given rise to emission increase collectively.

As can be seen from the research which has been conducted so far throughout this paper, there can be seen a well-established cause and effect relationship between the drivers and the resulting pressures which have occurred as a result of them. These both contribute to the state known as OA, as touched on before. Thus, the degradation of quality of the environment can be divided into two main parts: ecosystems and water quality. Both of these have severe ramifications on wider ocean health and human population health as a whole.

First, looking at the state of ecosystems it can be seen that there are widespread levels as to the impact of OA on biodiversity and marine organism health. The difficulty which has presented itself on OA research is that it is hard to extrapolate the conditions on wider marine communities just from examining the response of individual species. Numerous researchers have pointed out that the response to increasing ocean acidity of individual organisms is able to be effective gauged, but the difficulty comes with understanding how these will impact the whole of future communities. Furthermore, it must also be noted that it becomes nearly impossible to have a single way to quantifiably measure the amount of degradation within all trophic levels of the entire ecosystem. As Sam Dupont and Hans Pörtner describe, “no single experiment can capture the complexity, so a variety of approaches will be needed. Single-species investigations will remain valuable…” (Dupont and Pörtner 429). However, on an issue as pervasive as OA, the study of individual species to represent the response of entire communities seems difficult to use in certain cases, as community response will undoubtedly be different than individual responses. Thus, there must other ways of measuring OA. Researchers Riebesell and Gattuso have stated that:

Understanding the impacts of ocean acidification at the level of communities and ecosystems, and assessing their consequences for ecosystem services, can therefore only be achieved through a combination of experimental approaches involving natural communities and field studies, taking advantage of natural gradients in key environmental parameters to substitute space for time (Riebesell and Gattuso 13).

What is currently known about the likely response to OA by individual species is that it will hit calcifying organisms the hardest, due to the lack of carbonate ions reacting with calcium present in the water. Organisms such as coral, shellfish-like clams, oysters, crabs, and lobsters are all impacted due to decreased ability to strengthen and build shells and skeletons, however, all marine will be impacted in some way, probably on their physiology (Harrould-Kolieb et al. 3).

Next, examining the state of water quality it can be seen that the most obvious of ramifications is the large increase in carbon uptake by oceans. The most predominant of issues within water quality is that of marine water mixing and the increase in other ocean issues that are caused by OA. The rising levels of ocean acidity is, “due to [its] large volume and the ability of seawater to buffer CO2, oceans have absorbed approximately half of all anthropogenic CO2 emissions to the atmosphere” (Pörtner 203). As can be seen from this, there has been significant amounts of carbon dioxide entering the water and this can have impacts especially on oceanic layers. The ocean is divided into layers and each has its own adapted organisms within it. Moreover, as ocean acidity increases there has become proof that, “the rate of exchange between surface and deeper waters could change, as could the long-term partitioning of CO2 between the atmosphere and the ocean” (Tans 31). With greater water mixing, the issue of ocean acidity becomes not just an issue of the upper layers, (where carbon uptake occurs more frequently) but it in turn will cause layers that would not have usually experienced increased carbon uptake, to undergo it. Another impact is that increased OA gives rise to numerous other marine issues. There has been well-documented evidence that increased carbon dioxide levels within oceans are also working in tangent with the other issues such as coral bleaching, hypoxia, warming and eutrophication (Pörtner 203). These other major ocean issues have their own drivers and pressures but what is interesting about OA is that it where it is found, many other issues are similarly found there. As well, it is understood by researchers such as Kristy Kroeker that in order to effectively examine OA, other marine issues issues must be simultaneously examined as well to examine marine response (Kroeker et al. 1983). Taken together, the states of biodiversity and water quality are the most significant results of the OA issue and thus, they must not be neglected when trying to discover the extent of this issue.

The changes which have been examined within the states impacted by OA all have wider societal impacts. Under the DPSIR model, it is these impacts which must be addressed and analyzed to effectively find ways to mitigate this issue. Further, it can be understood that there must be highly complex analysis of these impacts in order for OA to have steps taken away to solve it. As pointed out by Riebesell and Gattuso, “because of the urgency of the issue, it is important to pay special attention to aspects that matter most to human societies, that is, those that relate to ecosystem services and may lead to management options and policy advice” (Riebesell and Gattuso 14) One of the impacts which will undoubtedly have a significant effect on human well-being would be coral reef degradation. The degradation of coral reefs is already having serious ramifications for human well-being as decreased coral reefs cause habitat loss for fish and shellfish, as well as loss of breeding grounds as well. Humans have always been reliant upon oceans for millennia but the ocean is a massive resource for food that many global populations are reliant on, “more than 450 million people from 109 countries live close to coral reefs, which provide important sources of ecosystem goods and services for these communities” (Pandolfi et al 418). The loss of such an important resource as a result of OA would be detrimental to not only global human health, but to the socio-economic fabric which as become dependant upon the ocean. The only way which OA will be able to be mitigated is through aggressive policy and societal responses.

Under the DPSIR model, the last lens of analysis is the responses to these forces. Responses should be done at every level to attempt to mitigate the effects of OA and will directly result in how successful the end result would be. Globally, the problem of OA has become the forefront focus of marine policy creation as its far-reaching impacts become increasingly able to be seen. It is best summarized as “translating the wide range of responses to ecosystem consequences, management actions, and policy decisions requires a synthetic understanding of the sources of variability in species responses to acidification and the corresponding levels of certainty of the impacts” (Kroeker et al 1884). The most obvious and effective of responses it to must limit and reduce carbon dioxide emissions. Through agreements such as the Kyoto Protocol which set emissions targets, there has been an international push for environmental policy. However, with major nations subsequently opting out, or not participating there has been a step backward (Bille et al 764). As has been declared by numerous scientists, there must be widespread efforts to keep warming of the globe under a two degrees target. However, as international accords are abandoned and an increasing narratives being pushed that climate change is false, it seems that the wrong direction is being headed towards. However, scientists are pushing for change, as well as the general public as this issue becomes discussed more and as the severity of the issue is uncovered. Social movements have raised awareness as more and more of the population becomes aware of this issue. There has become increased awareness surrounding other solutions such as marine ecosystem protection from various stressors, restoration of past degraded ones and the development of last-resort technologies for the worst-case scenario (Bille et al 775). The push towards policy response and the level of effectiveness requires success where continued failures have occurred and only through systemic change at all levels will this effectively occur and ocean acidification will be mitigated.

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