User:Ricarda L/sandbox

Impacts on the environment
To understand climate trends in the past, present and future, natural variability must be taken into account. Climate variability refers to the annual variations in climate conditions, such as temperature and precipitation, within their normal range. Factors which contribute to natural variability in Puerto Rico are for example phenomena like the El Niño Southern Oscillation or periodic events, such as volcanic eruptions. These natural factors are summarized under the term "internal climate variability" and are always present in the climate system (https://climateknowledgeportal.worldbank.org/country/puerto-rico/trends-variability-historical ).

In contrast to that, anthropogenic emissions of greenhouse gases, changes in atmospheric concentrations (e.g. CO2, methane) and land surface changes are a different influence on the climate system. In order to identify climate change signals, it is crucial to distinguishing these human-induced changes from natural variability. Climate change signals can be observed as changes in the magnitude of variability as well as systematic trends over time. In summary, variability is a natural feature of the climate system and its understanding is fundamental for identifying signals of anthropogenic climate change (World Bank Climate Change Knowledge Portal, n.d.) (https://climateknowledgeportal.worldbank.org/country/puerto-rico/trends-variability-historical ).

The diagram on the right shows how internal climate variability and mean temperature trends have shifted over the last 50 years in Puerto Rico. It becomes evident that the mean temperature has significantly increased within this time span.

Changes in Climate Parameters
Puerto Rico has a tropical climate with moderately high temperatures and high humidity all year round (https://www.drought.gov/states/puerto-rico / https://drought.unl.edu/archive/plans/Drought/state/PR_2015.pdf ). According to the US Environmental Protection Agency, it is more affected by climate change than any other country in the world (https://19january2017snapshot.epa.gov/sites/production/files/2016-09/documents/climate-change-pr.pdf). The Puerto Rico Climate Change Council (PRCCC) has identified seven climate parameters that are unique to Puerto Rico, including air temperature, precipitation, extreme weather events, tropical storms and hurricanes, ocean acidification, sea surface temperature and sea level rise (Ezcurra & Rivera-Collazo, 2018).

Air temperature
The mean annual temperature in Puerto Rico has increased over the last 100 years, from about 23 °C in 1921 to 25 °C in 2021 (https://climateknowledgeportal.worldbank.org/country/puerto-rico). The World Bank Climate Knowledge Portal publishes graphs which illustrate these changes in the mean temperature. Projections for future air temperature in Puerto Rico are consistent with global patterns. Compared to other islands in the Caribbean, the country shows a stronger trend of warming air temperature (https://www.sciencedirect.com/science/article/pii/S1296207417306441?casa_token=95ygJ3_W9foAAAAA:qV9taI80BSmqxEJyrC25F9MVmJTwI6dFrm_doQMr13bLXcZeqZBV7WFyUW85IX-jP3LJmiYX6Q). Ezcurra & Rivera-Collazo, 2018

The central regions of Puerto Rico, which are at higher elevations, are experiencing faster warming than other parts of the island. In addition, urban areas like San Juan, are experiencing the so-called urban heat island effect (UHI). This means that they are warming faster than rural or vegetated regions. Studies in San Juan have shown that the UHI effect is permanent due to urban extension and leads to a temperature increase of over 4 °C compared to surrounding rural areas. This trend of greater urban warming is expected to continue, with San Juan reaching an average temperature of 27°C by 2050, an increase of 1.5°C over 1950 levels. (https://www.sciencedirect.com/science/article/pii/S1296207417306441?casa_token=95ygJ3_W9foAAAAA:qV9taI80BSmqxEJyrC25F9MVmJTwI6dFrm_doQMr13bLXcZeqZBV7WFyUW85IX-jP3LJmiYX6Q).

Extreme weather events
The number of days with maximum temperature is increasing in the country, while days with minimum temperature are decreasing. During the early 20th century there were approximately 100 days per decade which reached temperatures of over 32.2°C. In 2010, however, the same number of heat days were reached within one year. (https://www.sciencedirect.com/science/article/pii/S1296207417306441?casa_token=95ygJ3_W9foAAAAA:qV9taI80BSmqxEJyrC25F9MVmJTwI6dFrm_doQMr13bLXcZeqZBV7WFyUW85IX-jP3LJmiYX6Q)

Precipitation
Being a tropical island, precipitation rates are naturally very high, especially in the north and central regions, which receive between 3000 – 4000 mm of rainfall every year. https://agupubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1029/2019GL082077 Within the country, rainfall varies from region to region due to topography and geography in relation to trade winds and oceanic circulation. Climate change is predicted to exacerbate these regional differences. For example, in some areas such as Old San Juan, there is a long-term trend towards a decrease in precipitation. This decline is expected to continue in future projections. In contrast, the southern regions of Puerto Rico, which have been drier in the past, show a positive trend in precipitation. The seasonal distribution of precipitation is also expected to become more pronounced, with wetter winters and drier summers. Overall, future projections indicate a further decrease in precipitation. (https://www.sciencedirect.com/science/article/pii/S1296207417306441?casa_token=95ygJ3_W9foAAAAA:qV9taI80BSmqxEJyrC25F9MVmJTwI6dFrm_doQMr13bLXcZeqZBV7WFyUW85IX-jP3LJmiYX6Q)

Concerning intense rain events, heavy rainfall has increased by 20% on average in North America, with the largest increase in the wettest regions. Puerto Rico has seen a 37% increase in heavy precipitation. There is only limited data available for future projections, which leads to conflicting forecasts for extreme precipitation in the country. However, the overall projections for the Caribbean region suggest a higher incidence of extreme precipitation events despite a decrease in total rainfall. In other words, rain will be less frequent but more intense. (https://www.sciencedirect.com/science/article/pii/S1296207417306441?casa_token=95ygJ3_W9foAAAAA:qV9taI80BSmqxEJyrC25F9MVmJTwI6dFrm_doQMr13bLXcZeqZBV7WFyUW85IX-jP3LJmiYX6Q)

Water ressources
Potential impacts on water resources in rain-fed areas of the Caribbean include higher precipitation extremes, greater seasonal variability in water runoff, a higher likelihood of prolonged dry spells and an increased risk of droughts and floods. In this context, prolonged dry periods and increased evaporation can lead to a decline in lake levels. This is problematic as they are essential as a source of freshwater supply. As water demand increases, groundwater use is expected to increase. This is especially true in dry months when surface sources decline. Prolonged dry periods could also lead to reduced soil moisture, resulting in an increased need for irrigation in agriculture. https://www.sciencedirect.com/science/article/pii/S0378377409000316?casa_token=n-roGl49_SAAAAAA:JtQWlv5c2O91klkDL4aBw8nBezHH0R8uXp1wujA8TodYUbCGdQOwiAENBzt9xb6GwN2SZ4f_Jw

Sea surface temperature
Over the last century, the surface temperatures of the Caribbean Sea have warmed by 1.5 °C. The warming of the sea surface is faster on the Caribbean coasts of Puerto Rico than on the Atlantic coasts. In addition, temperatures below the water surface are rising faster than surface temperatures. Researchers estimate that there will be an increase of more than 1 °C within 50 years. This would mean that temperatures would exceed the threshold for coral bleaching in about one third of the year. In addition, the threshold for the formation of deep convection storms will be exceeded throughout the year. (Ezcurra & Rivera-Collazo, 2018).

Sea level rise
The rate of sea level rise (SLR) in Puerto Rico has been measured at 1.7 mm yr−1 based on historical records from tidal gauges since 1900, which is consistent with global trends. However, recent satellite data from 1992 onwards shows that this rate has almost doubled to 3.2 mm yr−1. Projections for the future SLR in Puerto Rico are similar to global estimates, with the National Oceanographic and Atmospheric Administration (NOAA) recommending updated bounds of 0.3 m to 2.5 m for end-of-century projections. The Caribbean region, including Puerto Rico, is particularly vulnerable to coastal flooding due to SLR. (Ezcurra & Rivera-Collazo, 2018).

Ocean acidification
As more carbon dioxide (CO2) is released into the atmosphere, the ocean absorbs more CO2, leading to a decrease in pH and carbonate saturation of the ocean. This process is called ocean acidification and it negatively impacts marine life and geological processes through reducing calcification rates and mineral precipitation. Puerto Rico experiences similar trends as the rest of the world, with decreasing average pH and carbonate saturation state. The rate of decline for aragonite saturation states in Puerto Rico is currently at 3% per decade and is expected to continue with ongoing emissions (Ezcurra & Rivera-Collazo, 2018).

Tropical storms and hurricanes
Since 1995 the North Atlantic area has experienced an increase in hurricane activity. However, this increase cannot be fully explained by human-induced climate change, but may also be influenced by natural variations. In general, it is difficult to predict future hurricane activity, especially on a regional scale, due to uncertainties in modelling parameters. However, many studies suggest that hurricanes worldwide will become less frequent but more intense, with higher wind speeds and heavier rainfall, resulting in greater destructive power. (https://www.sciencedirect.com/science/article/pii/S1296207417306441?casa_token=95ygJ3_W9foAAAAA:qV9taI80BSmqxEJyrC25F9MVmJTwI6dFrm_doQMr13bLXcZeqZBV7WFyUW85IX-jP3LJmiYX6Q). Ezcurra & Rivera-Collazo, 2018

In Puerto Rico, hurricanes Irma and Maria in 2017 were an example of these predicted climate change impacts that had devastating impacts in the Caribbean. One consequence of this is damage to the coral reefs off the country's coasts which dissipate wave energy. The lack of protection from the reefs, leads to an increased risk of damages caused by winter swells, resulting in coastal erosion and sediment displacement. The southern part of the island is particularly vulnerable to Atlantic hurricanes. In the future, rising sea surface temperatures are likely to lead to more intense rainfall, winds and storm surges (https://www.sciencedirect.com/science/article/pii/S1296207417306441?casa_token=95ygJ3_W9foAAAAA:qV9taI80BSmqxEJyrC25F9MVmJTwI6dFrm_doQMr13bLXcZeqZBV7WFyUW85IX-jP3LJmiYX6Q). Ezcurra & Rivera-Collazo, 2018

Ecosystems
Despite the relativly small size of the country there are several different ecosystems in the country: coastal and marine, dry forests and rainforests, the Puerto Rican karst, and mountainous areas (https://climateknowledgeportal.worldbank.org/country/puerto-rico/climate-data-historical).

Climate change is expected to have synergistic effects on ecosystems and species in Puerto Rico. This means that systems already under stress will be exposed to additional stressors that exceed their adaptive capacity, resulting in loss of habitat, adverse changes in structure and function, or reduced benefits to society. While certain ecosystems and species may be better able to adapt to the changing environment, others may have difficulty coping with the new conditions. ( https://pr-ccc.org/wp-content/uploads/2014/08/PRCCC_ExecutiveSummary.pdf )

Dry and Rainforest
Today, about 40% of Puerto Rico's land area is covered by forests, which consist mainly of young mixed forests. These forests provide an important habitat for numerous plant and animal species and are essential for nearly 4 million people, especially for community water supplies, agriculture and industry. They are also increasingly used as recreational areas. The changes in Puerto Rico's forests serve as a valuable model for understanding similar changes on other tropical islands as a result of human expansion. The island's forests have changed dramatically over the past two centuries as a result of the introduction of economically important crops and deforestation for grazing and charcoal production. Today, forests and old agricultural lands are disappearing due to urbanization and development. Puerto Rico's forests are highly diverse in terms of location and type, and the diversity of forest types has yet to be fully documented (https://data.fs.usda.gov/research/pubs/iitf/iitf_gtr_35.pdf)

Forests are affected and pressured by climate change due to higher air temperatures, changes in precipitation, more intense wind and water events, and sea level rise. All of these factors are changing species composition and forest structure due to habitat changes. ( https://pr-ccc.org/wp-content/uploads/2014/08/PRCCC_ExecutiveSummary.pdf ).

Wetlands
Puerto Rico has a variety of freshwater and marine wetland ecosystems, from coastal seagrass and mangrove ecosystems to numerous freshwater wetlands and high-elevation cloud forests. These wetlands are incredibly productive and host a variety of rare plant and animal species. They also play a critical role in supplying water to downstream human communities. When runoff from the mountains reaches the coast, it contributes to the formation of vital ecosystems in rivers, coastal waters, and estuaries that serve as breeding and nursery habitats for a variety of fish, crustaceans, and other organisms. ( https://data.fs.usda.gov/research/pubs/iitf/iitf_gtr_35.pdf )

In Puerto Rico and the Caribbean in general, palustrine and estuarine ecosystems are vulnerable to climate change impacts because of the relationship between hydrology and wetland structure and function. Most of the wetlands in Puerto Rico are located along the coast, with palustrine wetlands largely adjacent to estuaries or coastal ecosystems, resulting in interactions between the different systems. ( https://www.drna.pr.gov/wp-content/uploads/2022/10/PR_StateOfTheClimate_2014-2021_PRCCC-09-2022.pdf )

Bioluminescent Systems
In Puerto Rico, bioluminescent bays and lagoons are distinct and rare ecosystems where bioluminescent algal species accumulate and emit light. These systems are generally shallow and small with narrow exits to the sea, resulting in long residence times in the water and large populations of algae. Factors such as water circulation patterns and wind can also contribute to maintaining high species diversity in these ecosystems. ( https://www.drna.pr.gov/wp-content/uploads/2022/10/PR_StateOfTheClimate_2014-2021_PRCCC-09-2022.pdf )

Climate change can stress bioluminescent systems, especially through heavy precipitation, storms, and hurricanes. These factors can lead to an increase in land runoff, which can result in higher levels of sediment and nutrients in the water. In other words, water quality can change due to changes in sedimentation, productivity, and the frequency and magnitude of salinity changes. In addition, phytoplankton organisms may be affected by warmer temperatures associated with global climate change. ( https://pr-ccc.org/wp-content/uploads/2014/08/PRCCC_ExecutiveSummary.pdf )

Shorelines
Puerto Rico has two main types of coasts: beaches (30%) and vegetated coasts, mainly covered by mangroves (28%), although other plants are found in the dune areas. Rocky coasts represent 10% of the island's coastlines and are composed of different types of rocks. The transition from agriculture to industry in the mid-20th century resulted in numerous changes to the coastline, such as the construction of port facilities and breakwaters. Urbanization and residential development have also contributed to the hardening of the shoreline, resulting in changes in sediment transport and erosion. The spread of fortified shorelines poses a significant threat by reducing natural coastal protection and promoting erosion, which is likely to be exacerbated by climate change, including the increasing intensity and frequency of storms and sea level rise.

https://www.drna.pr.gov/wp-content/uploads/2022/10/PR_StateOfTheClimate_2014-2021_PRCCC-09-2022.pdf

Marine Systems
Puerto Rico's marine ecosystems consist of coral and seagrass habitats, bays, and small islands that host a number of valuable resources such as fisheries and marine mammals. (Effects of climate change will be added later).

https://www.drna.pr.gov/wp-content/uploads/2022/10/PR_StateOfTheClimate_2014-2021_PRCCC-09-2022.pdf

Society and culture
Puerto Rico has a long and culturally rich history, spanning more than 5,000 years of social processes. https://www.sciencedirect.com/science/article/pii/S1296207417306441?casa_token=95ygJ3_W9foAAAAA:qV9taI80BSmqxEJyrC25F9MVmJTwI6dFrm_doQMr13bLXcZeqZBV7WFyUW85IX-jP3LJmiYX6Q ). Climate change is considered a major threat to severely affect the physical evidence of this history. This is due to rising air temperatures, which are associated with an increased rate of degradation of artefacts and decay of organic material. Another reason is the changes in precipitation, which may make some regions drier or wetter and thus change the conditions for the materials, for example by making them more prone to fire.

In order to preserve Puerto Rico's cultural heritage, its vulnerability must be assessed so that management plans can be created that include strategies to increase resilience and adaptability. Early identification of sites at risk is crucial for the creation of historical records and collections. A useful tool for the prevention of cultural heritage sites is community participation, i.e. the use of citizen science to monitor areas and provide feedback on their significance.

A study done by Mendez-Tejeda et al. (2021) has shown that the public awareness of climate change amongst citizens in Puerto Rico has increased after the devastating effects of Hurricane Maria in 2017. According to this study, non-profit institutions and the scientific community are more trusted by Puerto Ricans compared to state authorities. The study also revealed that 85% of citizens believe that public policies on global climate change should be directed by the state, including federal, state, and municipal governments. ( https://www.scirp.org/journal/paperinformation.aspx?paperid=108747