TEHRAN – Marked on June 29, the International Day of the Tropics celebrates the extraordinary diversity of the tropics, highlighting challenges and opportunities tropical nations face.

The day provides an opportunity to take stock of progress across the tropics, to share tropical stories and expertise, and to acknowledge the diversity and potential of the region.

The Tropics are a region of the Earth, roughly defined as the area between the tropic of Cancer and the tropic of Capricorn. Although topography and other factors contribute to climatic variation, tropical locations are typically warm and experience little seasonal change in day-to-day temperature.

An important feature of the Tropics is the prevalence of rain in the moist inner regions near the equator, and the seasonality of rainfall increases with the distance from the equator. The tropical region faces several challenges such as climate change, deforestation, logging, urbanization, and demographic changes.

The tropics are home to around 80 percent of the world’s biodiversity. They host nearly 95 percent of the world’s mangrove forests by area and 99 percent of mangrove species.

Unfortunately, the first global assessment of mangroves by the International Union for Conservation of Nature (IUCN) has classified mangrove forests in the Persian Gulf as vulnerable (VU) overall.

The mangrove forests are classified as ‘vulnerable’ in Changes in Geographic Distribution, ‘least concern’ in Restricted Geographic distribution, ‘least concern’ in Abiotic components, and ‘least concern’ in Biotic components of ecosystems, ISNA reported.

The IUCN assessment results can be the basis for national and regional decision-making and intervention. The results indicate that planning, ongoing monitoring, and integrated management of these ecosystems should be prioritized. Otherwise, these ecosystems are likely to move into a more dangerous category.

Mangrove ecosystems are crucial for biodiversity conservation, providing essential goods and services to local communities and mitigating the impact of climate change. For this reason, understanding the risk of ecosystem collapse has serious socioeconomic implications.

According to data published in various sources, the total extent of mangrove forests in the Persian Gulf and Sea of Oman is about 250 square kilometers, with Iran having the largest share with 138 square kilometers.

Mangrove forests in Iran mostly consist of the Avicenna marina, known as Hara, named after the 11th-century great Iranian scientist Avicenna, or Abu-Ali-Sina. Hara forest area covers more than 27 thousand hectares.

The forests spread from Nayband Bay in the southwestern Bushehr province to Govater Bay in the southeastern Sistan-Baluchestan province on the coast of the Sea of Oman.

More than 90 percent of these forests, both in terms of quality and quantity, are located in the southern Hormozgan province, such as Khamir Port and Qeshm Island, although there is a part in the Khor Azini site, in Sirik county in Hormozgan, which hosts the Rhizophora mucronata species.

Contamination from oil, gas, and petrochemical industries in the vicinity of mangroves, effluent from aquaculture farms, timber harvesting, livestock grazing, and substandard construction, unregulated tourism, plant pests, reduced freshwater inflow due to dam construction, and agricultural pesticides are among the main challenges faced by mangroves.

Threats menacing mangroves are evolving rapidly:  degradation from wood exploitation, deforestation for agriculture and shrimp farming, and indirect impacts from dam construction altering freshwater and sediment fluxes. Today, mangroves face additional challenges due to climate change, including sea-level rise and an increased frequency and severity of cyclonic storms.

According to the first global assessment, fifty percent of Mangrove Ecosystems units are at risk of collapse (in the IUCN threat categories of Vulnerable (VU), Endangered (EN), or Critically Endangered (CR); equally, they represent 50 percent of the world’s mangrove area. And one out of five are at severe risk of collapse (either Endangered or Critically Endangered). The other units are Near Threatened (NT), Least Concern (LC), or Not Evaluated (NE).

Mangrove ecosystems are exceptional in their ability to provide essential ecosystem services to people, including coastal disaster risk reduction, carbon sequestration and long-term storage, and ecological support for fisheries and biodiversity.

The Human System

Tropical nations have made significant progress but face a variety of challenges that demand focused attention across a range of development indicators and data in order to achieve sustainable development.

By 2050, the region will host most of the world’s people and two-thirds of its children.

Consistent with the higher levels of poverty, more people experience undernourishment in the Tropics than in the rest of the world.

The proportion of the urban population living in slum conditions is higher in the Tropics than in the rest of the World.

Mangrove forests in Iran

According to a study by researchers at the National Institute of Oceanography, mangrove ecosystems in the northern Persian Gulf are facing a range of environmental and anthropogenic pressures.

Mangrove forests in Iran mostly consist of the Avicenna marina, known as Hara, named after the 11th-century great Iranian scientist Avicenna, or Abu-Ali-Sina.

The study assesses the ecological dynamics of the Mangroves of Dayyer City (MDC) in the northern Persian Gulf using a multidimensional approach involving satellite-derived, drone-based, and field-measured data.

Satellite imagery from Google Earth (2011–2022) reveals fluctuations in the MDC area, with notable afforestation efforts until 2018, followed by rapid degradation.

The mangrove forest, initially covering 2.2 hectares in 2011, expanded to 3.2 hectares by 2015 due to afforestation efforts but declined to 1.7 hectares by June 2022.

The construction of a nonstandard road and a bridge in 2018 obstructed freshwater flow from upper areas, emerging as a major factor responsible for the degradation.

Drone-based observations in March 2023 provided a detailed map, revealing that 44 percent of healthy mangroves had been damaged. Field measurements conducted in November 2023 showed higher salinity levels at MDC compared to other adjacent mangrove areas.