Mangroves in Australia

Introduction of Mangroves

The world today is comprised of various ecosystems that fill the planet with a diverse collection of plants and animals. Mangrove forests are one of the most unique environments and support a variety of organisms. These forests are found in tropical and subtropical latitudes. In Australia, mangroves cover over 18,788 km of area, the 3^rd largest area of mangroves following Indonesia and Brazil. Mangroves trees and shrubs inhabit the coast and are complex in both structure and diversity (1).  Australia experiences varying rainfall and temperatures throughout the country, resulting in a large diversity of plants and animals. Australia’s mangrove plants today reflect the numerous changes that have occurred over the past millions of years. Due to continental movements, mangrove communities have been broken then later rejoined, resulting in rich mangroves flora (2). However, due to human impact, particularly land clearing and urban development, mangroves are rapidly decreasing. Because they are both rich in biodiversity and beneficial to humans and the Earth, mangrove conservation is an environmental priority, and changes must be implemented to help preserve their existence.

Description of Mangrove Forests

Historically, mangroves forests contain tress and shrubs that are located between the land and the sea, where the species are able to survive in the salt environments and tidal inundations. Despite the harsh conditions, the mangrove supports the coastal food chains and provides a habitat for a variety of organisms (1). In terms of mangrove tree species, however, these forests are lacking in diversity due to the salt environment, and as result, only a few are able to survive due to adaptations. For example, mangrove trees use roots as a source of nutrients as well as support. For some, the roots are able to grow despite the lack of oxygen in the water, while others have pneumatophore roots, which stick out of the mud in order to take in air. The roots are pencil-like and anchor the trees down into the ground to protect from the tidal movements. In addition, the leaves of mangrove trees are able to secrete salt that has been absorbed from the water (3).  The sediment that washes in and stays behind is filled with nutrients, creating an ecosystem thriving with other life. Because the mangrove areas are often protected from high-energy waves, many animals use them as places to raise their young as well as feeding-grounds (1). In Australia, the mangroves contain a total of 70 species of crustaceans, 70 species of fish, 230 birds, and a few mammals such as rats (4). However, mangroves today are no longer as abundant and biologically rich as they were in the past due to direct and indirect human impacts. Mangroves are being destroyed and cannot support such a variety of life as before.

Human Impacts

Beginning in the 18^th century with the arrival of Europeans, Australia’s coastlines began transforming and consequently, so did the mangroves. As population increased, the usage and development of land increased, resulting in a decrease in natural resources, including mangroves. As urban development increased, mangrove areas became used as wastelands and overtime, mangroves unfortunately were viewed as solely for this purpose. The area of Moreton Bay has seen a decrease in 20% of the mangroves in the surrounding coastal areas as a direct result of the developing nearby cities that used the mangroves as a landfill (5). However, the main threats to mangrove survival include land use, clearing of vegetation, and intensive agriculture (1).  

Conversion/Land-Use

The building of urban centers along Australia’s coast has become a big threat to the mangrove community. As trees are cut, the environment no longer is a viable ecosystem, and consequently, the animals that depend on a healthy mangrove are endangered. For example, the most common tree species in the mangrove, the Avicennia Marina, contains hollows within the tree that the Rusty Monitor crab lives in. Therefore, when the trees are gone, the crab no longer has a place to live. These particular crabs are now endangered species.

Vegetation/Agriculture

The clearing of vegetation leads to sediment build-up, which ultimately leads to the destruction of mangroves. Ironically, growing intensive vegetation requires pesticides, which affect mangrove health as well. Sugarcane plantations in Australia often use pesticides that are harmful particularly to the Avicennia Marina. From chemicals alone, 30 square kilometers of mangroves have been loss. Even though 20 tree species have been unaffected by pesticides, the Avicennia Marina compose 50% of the total mangrove area in Australia (5).

Future of Mangroves

The future of mangroves in Australia, and throughout the world is generally hard to predict due to the lack of long-term data on mangrove environments. The current status of mangrove species is relatively good and they are not at risk. This is largely due to the fact that the majority of mangroves in Australia are located in less populated areas in the North. However, even though land development occurs relatively less compared to other countries, the conservation of mangroves is still important because these coastal areas contain the greatest number of threatened species, and when development does occur, the effects are drastic and severe (1). In Darwin, Australia, a recent growth in population has caused a reduction of mangroves in surrounding areas by 2% (5). As a result, if population growth continues along the coast, mangroves will continue to be destroyed. However, the good news is that the mangroves that are not at threat are in pristine condition. Mangroves are included in 180 of Australia’s protected areas. Since the Coastal Zone Inquiry in 1993, which focused on the sustainable use and management of coastal areas, inappropriate clearing of mangroves has decreased and the general health of mangroves has improved (5).  If nothing is done to help the preservation of mangroves, overtime, the direct and indirect effects of population growth will destroy these environments.

Benefits to Humans

Mangroves provide beneficial ecosystem services as their roots serve as a nursery for marine life and trees create a habitat for birds and small rodents (6). Traditionally, the mangroves were used to produce medicine and tools. The bark and ashes were used for treating illnesses such as headaches, snakebites, and skin disorders. The Avicennia Marina had a hard wood that was beneficial in building boats, spears, and boomerangs (7). However, mangrove forests also are valuable for humans as they act help protect the Earth. Because mangroves are located between the sea and the land, they play important roles in shoreline protection. They are able to absorb energy from the wind and waves as well as protect the land from erosion, both crucial for protection from large storms such as hurricanes and tsunamis. A healthy mangrove coastline could dramatically reduce the impact and damage from such storms. Many of the fish in mangrove waters are economically important. 90% of Australia’s population eats seafood, and 67% of the country’s total seafood catch originate from mangroves. A decrease in mangroves therefore would hurt the fishing industry, which is vital for Australia’s economy (6).  In addition, research has begun on the potential of mangroves in helping mitigate climate change and global warming. Because mangroves can possibly become carbon-storing environments, this could lower the impacts of climate change (8).

Recommendations for the Future

Because Australia’s mangroves are not currently considered at risk and their status is relatively good, the future of mangroves rely on preservation, rather than rehabilitation. Restoration projects of mangroves often have mixed results due to failures in site selection and soil and planting techniques. In addition, the success of these projects relies heavily on funding, time, and level of expertise (9). Therefore, preservation of the current healthy mangroves is an effective solution in terms of time, labor, as well as success-rate. Because development of urban centers and the use of land for agriculture are practices that ultimately cannot coincide with mangroves, buffer zones need to be created to separate mangrove environments from these activities. Laws should be enacted and enforced so that these human activities can occur without interring with the status of the surrounding mangroves. Even though the Australian community generally is aware of the importance of mangroves to the Earth, it is crucial to educate the population on the numerous interactions that occur within mangrove environments and how one change can have multiple effects on other organisms.  Even though Australia has 180 protected areas containing mangroves, only 8% of the total mangrove populations are within these protected areas (1). To increase this percentage, mangroves within the nation’s borders should be assigned to different areas such as conservation zones, fisheries, or marine parks to ensure their protection. In addition, because global warming is such a prevalent environmental issue today, educating the public of the potential benefits mangroves may have in combating climate change can provide an incentive for people to becoming more willing to take action to preserve these forests.

Mangrove forests are the only ecosystem that exist between the land and the sea, and contain less species, than other forests, such as the tropical forest (5). However, they are extremely rich in diversity because of the large number of organisms that live in the environment the mangroves provide. They also serve as a buffer zone between the land and the sea, providing ecological and human benefits. Preservation of the mangroves in Australia today can help keep one of the world’s most unique ecosystems alive for the future generations to come.