Supporting services are the foundational processes that maintain the conditions necessary for all other ecosystem services to exist. Unlike provisioning or regulating services, their benefits to humans are indirect and long-term. Without supporting services, no other ecosystem service category could function.
Nutrients cycle through ecosystems continuously, moving between living organisms, soil, water and the atmosphere. The key biogeochemical cycles relevant to Environmental Science are:
Carbon moves through:
- Photosynthesis: $CO_2$ absorbed by plants
- Respiration: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy}$
- Decomposition: Dead organic matter broken down by decomposers, releasing $CO_2$
- Combustion: Burning releases stored carbon
- Oceanic absorption: Oceans dissolve atmospheric $CO_2$
Nitrogen is essential for proteins and DNA but must be ‘fixed’ from atmospheric $N_2$ before most organisms can use it.
| Process | Description |
|---|---|
| Nitrogen fixation | Bacteria (e.g. Rhizobium) convert $N_2$ to $NH_3$ |
| Nitrification | Bacteria convert $NH_3$ to $NO_2^-$ then $NO_3^-$ |
| Assimilation | Plants absorb $NO_3^-$ and incorporate into proteins |
| Ammonification | Decomposers break down organic N back to $NH_3$ |
| Denitrification | Anaerobic bacteria return $N_2$ to atmosphere |
Phosphorus has no atmospheric reservoir — it cycles slowly through rock weathering, soil, water and organisms. Phosphorus is a common limiting nutrient in freshwater ecosystems; excess inputs cause eutrophication.
Soil is a complex mixture of mineral particles, organic matter (humus), water, air and living organisms. Soil formation is an extremely slow process:
- 1 cm of productive topsoil can take 100–1000 years to form
- Soil organisms (earthworms, fungi, bacteria) break down organic matter, releasing nutrients
- Physical and chemical weathering of bedrock provides mineral components
- Organic matter (humus) improves water retention, aeration and nutrient content
Soil is the basis of:
- Terrestrial food production
- Freshwater filtration
- Carbon storage
- Plant growth that underpins all terrestrial food webs
Threat: Soil erosion, compaction, salinisation and acidification destroy soil structure far faster than it can be rebuilt.
Photosynthesis is the fundamental energy-capturing process that drives nearly all life on Earth:
$$6CO_2 + 6H_2O \xrightarrow{\text{light energy}} C_6H_{12}O_6 + 6O_2$$
Net Primary Productivity (NPP) measures the rate of photosynthetic energy fixation minus respiration losses — it determines how much energy is available to support all higher trophic levels.
STUDY HINT: Supporting services are sometimes called ‘habitat’ or ‘maintenance’ services. The key distinguishing feature is that they are indirect benefits — they maintain the platform on which all other services operate. Always connect them to a direct consequence (e.g. ‘nutrient cycling maintains soil fertility, which supports food production’).
