2. Publication Trends in Climate Change and Marine Biodiversity
This examined materials published in Scopus Index journal outlets from 2003 to 2023 (
Figure 21). It found that the number of articles studying climate change, marine biodiversity, and adaptation increased from about 2 publications to over 25 publications by the end of 2023. Overall, there has been a consistent rise in the number of publications addressing these topics. This increase can be attributed to the growing challenges faced by marine biodiversity due to the escalating impact of climate change.
Figure 21.
Trend in the number of publications on climate change and marine biodiversity adaptation.
This revealed that most publications (61.3%) consist of journal articles (
Figure 32). Additionally, a significant portion of the publications were in the form of reviews, bringing the total combined percentage of articles to over 80%. On the other hand, book chapters accounted for approximately 11% of the publications, indicating that the issue of climate change and marine biodiversity has not received much attention in this format. Similarly, conference proceedings have not extensively covered the topics of climate change and marine biodiversity adaptation. The Scopus Index accounted for a mere 4.1% of the publications, which could be attributed to the complexity and high financial costs of conducting such studies.
Figure 32.
Marine biodiversity adaptation and climate change publication outlets and research areas.
The studies conducted on marine biodiversity adaptation and climate change have been transdisciplinary, with many published regarding environmental science, agriculture, and biology. A substantial number of publications were also found regarding Earth and planetary science and social sciences. A transdisciplinary approach is crucial to addressing all aspects of this important research area, as it enables the consideration of multiple perspectives when tackling these issues.
As with other areas of scientific inquiry, researchers in the Global North have been more invested in climate change and marine biodiversity than Global South academics, judging by the volume of work produced, as seen in
Figure 43. This found that, in most cases, these studies were conducted by states with coastlines with the highest concentrations. These studies were conducted by the USA, the United Kingdom, Australia, Canada, France, and other states in the Global North. Very little has been done in Africa, with studies emerging in South Africa and several states in South America. Only a few states in South America have not explored the dynamics of biodiversity and climate change in that region. On the other hand, no studies have been conducted in many states on the west coast of Africa and in island states such as Madagascar. This could point to significant knowledge gaps in some regions. There are also significant knowledge gaps in the Arctic region. It is worth noting the considerable interest exhibited in this matter by Asian countries, including China.
Figure 43.
Publishing countries and collaborations between countries.
With regards to collaborations, there has been much collaboration between the North and North and very little to talk about between the North and the South. Most collaborating researchers were from the United States, which had collaborations with researchers from 66 countries; USA researchers have worked with researchers from 64 countries; Germany, 48 countries; and Australia and France, 47 countries. South African researchers collaborated with 28 countries, but none of the countries South Africa collaborated with are top publishers in the space.
3. Research Focus Area in Climate Change and Marine Biodiversity
Over time, there has been an evolution in the discussions about climate change, marine biodiversity, and climate change, as shown in
Figure 54. Climate change has been a central issue. There has been an acknowledgement that anthropogenic climate change has been responsible for multiple challenges affecting marine biodiversity. The work conducted thus far covers a range of issues that have transformed over time, given the evolving development within the climate change space.
Figure 54.
Trend in marine biodiversity and climate change, 2003–2023.
4. Impact of Climate Change on Marine Biodiversity
Chaudhary et al.
[37][36], one of the most cited scholars in the field of climate change and marine biodiversity, cite global warming as a key driver of climate change, which poses a challenge to marine biodiversity. The increase in sea surface temperatures, a topic that has been extensively researched in the field of climate change and marine biodiversity (
Figure 54), is believed to be responsible for latitudinal shifts in marine species. as temperatures rise, there has been a decline in species and species richness along the equator, with species moving towards the poles in search of more suitable habitats. These findings are supported by other scholars, such as Lin et al.
[38][37], who studied marine fish at various taxonomic levels and observed decreased species diversity at the equator, with the Northern Hemisphere having greater species diversity. In another study, Lin et al.
[39][38] found that the number of fish species with higher taxon and phylogenetic similarity decreases with latitude and ocean depth because of climate change. Lin and Costello
[40][39] also found that fish body size and trophic level increase with latitude because of climate change, likely because of changes in temperature and oxygen levels. On the other hand, Manes et al.
[41][40] noted that the projected increase in temperature could lead to the extinction of endemic marine and island species. These changes concern ecologists and the general population that relies on fish species, as they can limit access to critical protein sources, particularly in developing countries.
The increase in water temperature is blamed for altering water’s physical and chemical quality by causing changes in its oxygen levels. An increase in water temperature reduces the solubility of oxygen in ocean water. This has resulted in declining oxygen levels in ocean water and coastal waters, with serious adverse effects on biogeochemical cycles and global food security
[42][41]. According to Santos
[43][42], the decline in oxygen in sandy beaches has resulted in changes in pH, which have been linked to declines in species richness and the extinction of certain species.
Kim et al.
[44][43] conducted a comprehensive study of 741 scleractinian coral species from various parts of the world. They found that coral reefs are under immense pressure and vulnerability worldwide. The highest vulnerabilities were noted in the tropics, specifically in areas close to the equator in America; the Southwest African tropics; and areas around Australasia’s tropics, particularly in areas surrounding Australia. Coral in high latitudes was found to be less vulnerable than in the tropics. The extreme weather events unleashed by climate change and anthropogenic activities have contributed to this vulnerability. The tropics have witnessed several extreme weather events that threaten coral reefs, such as increased heatwaves. Holbrook et al.
[45][44] found that the occurrence of marine heatwaves is a challenge, causing the destruction of marine life and biodiversity and requiring adaptive measures to be put in place. This notion was supported by Welch et al.
[46][45], who argued that observed marine heatwave episodes have resulted in shifts in various marine species, including marine predators. The Southern Hemisphere and coastal species have been particularly affected, and the highest impact has been felt in areas that have experienced the highest intensity of marine heatwaves.
The fisheries were equally affected by marine heatwaves between 2015 and 2018, raising societal concerns. Marine heatwaves resulted in a drastic decline in fish stocks at a rapid rate and a decrease in other biodiversity
[47][46]. Consequently, it is easy to see that climate change has implications for the physiology of flora and fauna, ultimately affecting species richness and diversity.
Apart from suffering the harsh realities of global warming caused by anthropogenic-driven climate change, tropical species must also battle other extreme weather events that adversely impact coral reefs. Extreme weather events, such as tropical cyclones in some coral-reef-rich regions, like the Southwest Indian Ocean
[48][47], have faced tremendous tropical cyclones in the recent past, which could have damaged mangroves and coral reefs. High tides and high winds that often characterise tropical cyclones can physically damage coral reefs. Cheal et al.
[49][48] found that tropical cyclones of higher intensity have severely damaged large swaths of coral reefs in the Great Barrier Reef, with the worst expected as tropical cyclones are expected to increase their intensity with increased global warming
[50][49]. While Dixon et al.
[51][50] acknowledged the risk to coral reefs from tropical cyclones, they also noted the complexity of this risk as some downscaled data point to mixed results depending on the characteristics of cyclones in Western Australia.
In Madagascar, a study of the relationship between tropical cyclones and coral reefs found that tropical cyclones have decreased coral cover by 1.4% to 45.8% because of the damaging effect of wind and sea surges. Nevertheless, evidence shows that these corals have recovered and exceeded pre-cyclone periods after these tropical cyclones. Of concern are the adverse changes in the taxonomic structure of corals that emerge after a tropical cyclone, which could alter the aquatic ecosystem of coral reefs. In Taiwan, Lin et al.
[52][51] found the impact of tropical cyclones to be damaging in marine protected areas. This pattern is more or less the same in other areas with coral reefs, such as the Philippines
[53][52] and other areas in the Americas that are prone to tropical cyclones.
Changes in rainfall patterns also have an effect on ocean biodiversity. Changes in precipitation patterns can increase freshwater runoff and sediments in coastal waters. This can smother corals and disrupt their delicate balance with surrounding marine life. This is supported by Adam et al.
[54][53], who argued that rainfall patterns on land impact coral communities and their biodiversity. Haapkylä et al.
[55][54] argued that increased rainfall results in diseases for corals near the shore, which leads to biodiversity loss. Undoubtedly, the increased incidence of drought would affect biodiversity in coastal communities, as it will alter sea–land water interactions, resulting in changes in the chemical composition of the water. This could be compounded by the rise in sea levels, resulting in changes to the ocean ecosystem
[56][55]. Other land activities, such as global warming, can affect the productivity of sea turtles and their food chain in the ocean
[57][56].
Sea level rise, one of the global community’s challenges, is also challenging for marine biodiversity in many respects
[58][57]. Rising sea levels can significantly impact coastal ecosystems, including algal rims and plant communities in salt marshes. Part of the observed evidence of the destructive effects of rising sea levels is the destruction of mangroves, critical habitats for marine species
[59][58]. Mangroves have suffered the worst of various aspects of climate change, including rising sea levels, destruction from coastal erosion due to rising sea levels, and coastal flooding
[60,61,62][59][60][61].