Climate Change

The Earth´s climate has changed over many years due to natural processes such as volcanic eruptions, changes in the earth´s orbit, the tilt of its axis, the sun´s intensity, and the changes in naturally greenhouse gas concentrations in the atmosphere, nevertheless, since the Industrial Revolution, the main change in the atmospheric composition is associated to human activities such as the burning of fossil fuels like coal, oil, and gas to produce the whole energy on the world is the primary source of human-generated emissions.

Currently, the situation of the Earth to the changes in temperature, composition, and structure of ecosystems have been concerned for the rapid loss of geographic biodiversity, this change in the state of the climate and the variability on whether, alters the composition of the global atmosphere and it is called “Climate Change”, o know more about this process is necessary to introduce us to the basic concepts and the meaning of greenhouse gases (GHG).

Figure 1. Temperature changes from 1984 to 2018.

Basically, the atmosphere is the blanket of gases that surround Earth, it is held near the surface of the planet and extend to the exterior space, and it has a series of layers, each with its own specific traits, the lowest layer, called the Troposphere is the response to all the meteorological process related to the climate variations and the greenhouse effect, this layer has the air we breathe and the clouds in the sky, in fact, Troposphere is conformed for gases such as nitrogen (N), oxygen (O), and carbon dioxide (CO22), that are absorbed by organisms for their development. In this way, the climate is the constant product and the complex interaction among the atmosphere, ocean, ice layers, glaciers, continents and the whole ecosystems on the planet Earth.

Moreover, the greenhouse effect is the natural process that warms the Earth´s surface, when the sun´s energy reaches the Earth´s atmosphere on the Earth´s surface, ocean, and glaciers, some of this energy is reflected back to space and the rest is absorbed and re-radiated by the greenhouses gases (GHG), the primary GHG is carbon dioxide (CO22), nitrous oxide (N22O), methane (CH44), ozone (O33), perfluorocarbons (PFCs), hydrofluorocarbons (HFCs) and sulfur hexafluoride (SF6).6) and water vapor (H2O). These are the gases that concentrate the radiation that the earth's surface, oceans, and glaciers emit into space after being heated by solar radiation.

Even so, in the last decades, the concentrations of GHG and the 40% of CO2 in the atmosphere are increasing due to human activities and results in the rapid loss of forests, vegetation, ecosystems in the widest regions of the planet and it has reduced the capacity to remove high concentrations of GHG causing the increase of the Earth´s surface and sea surface temperature.

Figure 2. Synoptic charts and images of the layers of the atmosphere.
 Source: Cuadro Comparativo

Therefore, global climate change is the manifestation of climate change in different regions. As the Earth´s atmosphere heats up, it collects, retains, and drops more waters, changing weather patterns and making wet areas wetter and dry areas drier, higher temperatures worsen and increase the frequency of storms, floods, heatwaves, droughts, and glaciers melt into the seas. In some regions, the effects of climate change could be worse than others, but the whole planet has been affected.

Figure 3. Glacier melting from 1979 to 2019.
 Source: NASA

Despite forests being one of the most important ecosystems to absorb CO2, the second most important source to absorb this gas is the ocean and the organisms that absorb the CO2 for their development. Empirical data suggest that oceanic environments and marine ecosystems such as mangroves, sea-ice, salt marshes, and coral reefs are changing as a result of climate change and have been presented a higher extinction of organisms and the change in the function, structure, and composition in ecosystems to be exposed to human activities and climate change effects.

Regarding coral reefs, it has been reduced by the link between increased greenhouse gases, climate change, and regional-scale bleaching of corals, due to higher temperatures, acidification and it may cause weakening of coral skeletons and reduce the accretion of reefs, the frequency, and intensity of tropical storms, hurricanes, may also increase in some regions, leading to a shorter time for recovery between recurrences, the most pressing impact of climate change, are the bleaching events and disease that have already increase greatly in frequency and magnitude.

Photo 1. Coral Reefs, Puerto Morelos, Mexico. 2018.
 Photo: Ximena Lizaola.

On the other hand, coral reefs can recover from acute stresses and tolerate chronic stresses, but the problem is that the disturbances become more varied and frequent against a background of deteriorating conditions., Some models show an increase in temperatures and bleaching events, and it is based in two assumptions: that all coral respond identically to thermal stress, or the corals and their symbionts have inadequate phenotypic or genetic capabilities for adapting rapidly to changes in temperature. In some cases, high gene flow or connectivity will promote resilience and recovery from recurrent bleaching.

Since these problematics, the capacity of coral reef ecosystems to continue to generate the valuable goods and services, has to be better managed, this capacity requires improved protection of coral reef resilience, Marine Protected Areas are currently the best management tool for conserving coral reefs and other marine ecosystems, this tools could be protected coral reefs by overfishing, particularly of herbivorous parrotfish and surgeonfish, affects more than just the size of harvestable stocks, it alters the entire dynamic of a reef, reduce herbivory from overfishing, increased levels of disease, and excess nutrients can impair the resilience of corals and prevent their recovery following the disturbances and events. All those areas require a strong focus on reducing pollution, protecting food webs, and managing key functional groups (such as reef constructors, herbivores, and bioroders) for Coral Reefs Restoration Programs as insurance for conservation and sustainability.


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