What are Terrestrial Vegetated Ecosystems?

Terrestrial vegetated ecosystems are land-based natural environments that are covered by plants, which comprise about 29% of the total surface area of the Earth.

Terrestrial vegetated ecosystems can be classified into several categories based on different criteria, such as climatic conditions (i.e. temperature and rainfall), dominant vegetation types, soil type, geographical locations, etc.

Climate conditions
Dominant vegetation types
Tropical ecosystems
Forests
Temperate ecosystems
Shrublands
Arid and semi-arid ecosystems
Grasslands

Examples of two classification schemes of terrestrial vegetated ecosystems

What Kinds of Terrestrial Vegetated Ecosystems can be Found on Lantau Island?

Fung Shui Forest at Pak Mong

Fung Shui Forests

Wooded areas and native forests preserved behind villages owing to their fung shui significance. Villagers often plant economic plants like fruit trees, banyan trees, and bamboo along the edge of the forest to maximize their benefits. On Lantau, fung shui Forests can be found in places such as San Tau, Shui Hau, and Pak Mong.

Secondary Forests

Regrown forests after disturbance events (e.g. logging, agricultural clearance, fire) that have significantly impacted the original vegetation.

Secondary forest at Nong Ping

Montane Forests

Found in mountainous regions, typically at higher elevations that are influenced by cooler temperature.

Montane forest at Nei Lak Shan

Plantations

Forests that are established by active planting of trees or shrubs and often dominated by exotic species such as Acacia confusa and Lophostemon confertus.

Plantation at Shui Hau

Shrublands

Dominated by shrubs, which are woody plants that are shorter and smaller than trees. This terrestrial vegetated ecosystem is widely distributed in Hong Kong and is commonly found along hillsides. In natural succession, shrublands serve as temporary habitats, eventually being shaded out by trees as forests develop. However, human disturbances such as hill fires can disrupt this succession process, leading to a cyclical alternation between shrublands and grasslands.

Shrubland at Sunset Peak

Grasslands

Open areas dominated by grasses with few or no trees. Natural grasslands could be found in higher elevations where climatic and soil conditions restrict tree growth. In Hong Kong, many grasslands are primarily induced by human activities, particularly hill fires, as grasses can regenerate rapidly after fire.

Grassland at Lo Fu Tau

Why Are Terrestrial Vegetated Ecosystems Important?

Terrestrial vegetated ecosystems are fundamental components of our planet’s biosphere, playing a crucial role in sustaining life and maintaining ecological balance. Here are several reasons why they are important:

  • Supply of Food and Medicinal Resources
  • Biodiversity
  • Carbon Storage
  • Soil Maintenance
  • Water Regulation
  • Climate Regulation
  • Cultural and Recreational Value

Key Roles of Terrestrial Vegetated Ecosystems in Carbon Cycling

“Terrestrial vegetated ecosystems, particularly forests, play a crucial role in carbon storage and sequestration, absorbing approximately 2.6 billion metric tons of CO2 annually, which accounts for nearly one-third of global CO2 emissions from fossil fuels.” [1]

What is Ecosystem Carbon Storage?

It refers to the process of retaining carbon, often in organic form, in the vegetation and soils of various ecosystems. This ecosystem carbon storage can last for years, decades, or even centuries.

What is Ecosystem Carbon Sequestration?

It refers to the process of capturing and fixing CO2 from the atmosphere or carbon from other sources by the ecosystems. It plays a crucial role in mitigating climate change.

Where is the Carbon Stored in Terrestrial Vegetated Ecosystems?

Carbon is sequestered and stored in three major compartments of terrestrial vegetated ecosystems:

  • Living biomass – leaves, trunks, roots
  • Dead biomass – leaf litter, dead woods
  • Soil

How Can Terrestrial Vegetated Ecosystems Store and Sequester Significant Amounts of CO2 Effectively?

During the day, plants absorb CO2 from the atmosphere through photosynthesis and store the carbon in organic form within the plant tissues such as roots, stems, leaves, and fruits. While photosynthesis stops at night, plants continue to respire and release CO2 back into the atmosphere. However, because the magnitude of photosynthesis generally outweighs respiration on a daily basis, terrestrial plants and ecosystems generally function as net carbon sinks.

Soil can also store carbon when the input of soil organic matter from fallen leaves, branches, and plant roots is greater than the decomposition and loss of soil organic matter arising from respiration of soil microbes.

Grassland [3][4]

  • Cover 40% of the Earth’s land surface and store 34% of terrestrial carbon
  • Significant carbon sink due to its extensive root system, storing carbon in the soils
  • Able to sequester between 0.4 and 1.4 tonnes of CO2 per hectare annually with grassland restoration

Shrubland [5][6]

  • Cover around 10-20% of the Earth's land surface and store 10% of terrestrial carbon
  • An important carbon sink, particularly in regions where forests are unable to thrive
  • Able to sequester around 8.3 tonnes of CO2 per hectare annually

Forest [7][8]

  • Cover 30% of the Earth's land surface and store 39-45% of terrestrial carbon [9]
  • Largest carbon sink in the terrestrial ecosystem, storing most carbon in forest soil and living biomass
  • Able to sequester up to 11 tonnes of CO2 per hectare annually [10]
Carbon sequestration in forests [2]

Importance of Forest Conservation

Among the various terrestrial vegetated ecosystems, forests play a particularly crucial role in regulating the Earth’s climate. They serve as significant carbon reservoirs, with mature forests storing more carbon per unit area than any other types of vegetated ecosystems. Tropical forests alone account for approximately 30% of the world’s terrestrial carbon storage.

However, global forests face increasing threats from deforestation, degradation, and other disturbances. Approximately 27% of the world’s forest carbon sinks are found within protected areas [11], such as national parks. When these forest ecosystems are disturbed, the stored carbon is released back into the atmosphere as CO2, exacerbating climate change. On average, 8.1 billion metric tonnes of CO2 are released annually as a result of forest disturbances.

Forest conservation has been widely recognized in the international community as a critical measure in addressing climate change. At the recent COP29 in 2024, global leaders and stakeholders gathered to accelerate worldwide efforts to reduce deforestation, restore degraded forests, and harness the essential solutions that forests provide for mitigating greenhouse gas emissions and strengthening resilience [12]. In Hong Kong, forest conservation initiatives, including restoration projects and educational programs, have been implemented by both the government and NGOs. By fostering a deeper understanding of the benefits of healthy forest ecosystems, there is hope for ensuring that these vital ecosystems will thrive and continue to provide essential ecosystem services that benefit both the environment and society.

Reducing emissions from deforestation and forest degradation in developing countries (REDD+) [13]

REDD+ is a framework developed by the United Nations Framework Convention on Climate Change that helps developing countries in halting deforestation and forest degradation, while at the same time conserving and enhancing forest carbon stocks.

Global Forest Watch (GFW)

GFW, a project supported by the World Resources Institute and various UN agencies, is an interactive online forest monitoring and real-time alert system designed to empower people with the information they need to better manage and conserve forest landscapes. Some key features include deforestation detection, tree cover loss analysis, and visualization of spatially explicit data.

Reference

  1. IUCN. (2021). Forests and climate change. https://iucn.org/resources/issues-brief/forests-and-climate-change
  2. Minnesota Board of Water and Soil Resources. (2019). Carbon sequestration in forests. https://bwsr.state.mn.us/carbon-sequestration-forests
  3. Bai & Cotrufo. (2022). Grassland soil carbon sequestration. Science, 377,603–608.
  4. Shukla, et al. (2019). Climate Change and Land. Cambridge University Press. https://philpapers.org/rec/SHUCCA-2
  5. Keenan & Williams. (2018). The terrestrial carbon sink. Annu Rev Environ Resour 43, 219–243.
  6. Lu, et al. (2023). Frontiers in Plant Science, 14, 1120050.
  7. Harris, et al. (2021). Global maps. Nature Climate Change, 11, 234–240. 
  8. Pan, et al. (2011). A Large and Persistent Carbon Sink. Science,333, 988–993.
  9. Chen et al. (2021). IOP Conf. Ser.: Earth Environ. Sci.811. 012009
  10. International Monetary Fund. (n.d.). https://www.imf.org/en/Publications/WP/Issues/2021/02/19/Forest-Carbon-Sequestration-50279
  11. World Resources Institute. (2021). Forests absorb twice as much carbon as they emit each year. https://www.wri.org/insights/forests-absorb-twice-much-carbon-they-emit-each-year
  12. UNFCCC. (2024). Protecting Forests: Vital to Tackling the Climate Crisis. https://unfccc.int/news/protecting-forests-vital-to-tackling-the-climate-crisis
  13. United Nations Climate Change. (n.d.). What is REDD+?, https://unfccc.int/topics/land-use/workstreams/redd/what-is-redd#:~:text='REDD'%20stands%20for%20'Reducing,enhancement%20of%20forest%20carbon%20stocks