This document discusses soils and biodiversity. It notes that soils take a long time to form and are critical for food production. Soils contain a high level of biodiversity and play an important role in ecosystem services like water retention and carbon storage. Soil organic matter influences these services. The document then discusses soil health and managing soil carbon to boost agricultural productivity and climate change mitigation. It provides examples from Kenya, including threats to soils from land use change and a lack of soil policy. The key points are that soils are important for food production and ecosystem services, soil carbon management can provide benefits, and Kenyan soils face threats with limited policy protection.

1. Gachene CKK
Dept of Land Res Mangt &AgricTechnology
University of Nairobi
BIODIVERSITY AND ECOSYSTEMS
SERVICES AND SOIL FERTILITY

2. Soils – basic facts
 It can take up to 1 000 years to form one centimeter of soil.
 95 percent of our food is directly or indirectly produced on our soils.
 A shortage of any one of the 15 nutrients required for plant growth
can limit crop yield.
 It is estimated that soils can sequester around 20 PgC (petagrams of
carbon) in 25 years, more than 10 percent of the anthropogenic
emissions
 Nowhere in nature are species so densely packed as in soil
communities.
 Over 1000 species of invertebrates may be found in a single m2 of
forest soils.
 Many of the world’s terrestrial insect species are soil dwellers for at
least some stage of their life-cycle.

3. The benefits human populations derive, directly or indirectly from soil
ecosystem functions
Classification Services
Supporting services e.g retention and delivery of water and nutrients for plants
Soil organic matter is a key attribute which influences soils’
capacity to support ecosystem services.
Regulating services Soils have an essential role in climate regulation since soil
carbon is the terrestrial biosphere’s largest carbon reservoir
Provisioning
services
Soils are the basis of food and fibre production, water availability,
and are of vital importance to recharging water supplies. SOM is
necessary to both these services because it influences nutrient
and water availability and soil structure
Cultural services heritage sites, archaeological preserver of artefacts
spiritual value, religious sites, and burial grounds
Habitat habitat for soil biodiversity; gene pools

4. Soil health
• SH considers the physical, chemical/biological properties of
the soil and the disturbance and ameliorative responses of
land managers
• Soil health also describes the capacity of a soil to meet
performance standards relating to nutrient and water
storage and supply, biological diversity and function and
resistance to degradation.
• The most important of these manageable services include
BNF, other symbiotic and beneficial organisms, nutrient and
moisture supply, carbon storage and protection from
erosion.

5. Managing Soil Carbon for Multiple Benefits in
Smallholder Farming Systems
• Soil carbon can be managed to enhance a range of ESs
• Increasing the SOM of degraded soils can boost
agricultural productivity, sequester CO2, enhance soil
microbial growth and activities and improve water
capture and retention.
• Soil carbon stocks are highly vulnerable to human
activities.
• They decrease significantly in response to changes in LC
and LU such as deforestation and increased tillage

6. 0
2000
4000
6000
8000
10000
12000
forest agricultural grassland shrubland
Areainsqkm
Land use type
Change in LU from 1995 to 2004
1995
2004

7. LTRFC was selected for this study because of its uniqueness and the alarming rate at which this rare forest is
disappearing
very fragile soils
rare in Kenya to have a lowland evergreen riverine tropical forest.
quite diverse flora and comprise a mix of pan African species of western and central Africa rainforest species
and eastern and coastal forest endemic species, with at least 10 rare woody plant species.
two very highly endangered primates; the Tana River red colobus (Colobus badius rufomitratus) and Tana River
mangabey (Cercocebus galeritus galeritus) from extinction. .
The Disappearing Forest: Lower Tana River Forest Complex, Coastal
Kenya

8. Soil carbon gains can be achieved in two ways:
 first, by applying management strategies and technologies
that reduce losses of existing soil carbon
 second, by applying sustainable management techniques that
increase the levels of carbon in soils, particularly degraded
agricultural soils
However, in SH farming systems, alternative uses of crop
residues for fodder and fuel result in less carbon being
returned into the soil

9. Opportunity to use existing mechanisms to
encourage active management of SC
- LU planning that excludes vulnerable soils from land uses
that lead to SOC losses
- Promotion of proper SF management practices to protect
and enhance SOM as an essential element of good soil and
environmental quality
- Promotion of sources of plant nutrients (e.g. cover crops,
legumes, Biofix (Kenya, Uganda, Rwanda, Malawi, Ghana,
Zambia) that enhance SOC stocks.
- Integration of several crops in a field at the same time – increase
SOM, soil biodiversity and soil health

12. for erosion and weed control, moisture
conservation and enhanced bological activities

14. Currently there is no policy on soil health in Kenya
A cross-policy analysis on existing Kenyan legislation that is
related to soil threats and its support functions showed that:
 Four soil threats, namely; soil compaction, decline in
soil biodiversity, salinisation and floods were not
addressed in any of the 20 legislative policies that were
analyzed.
 Other soil threats, such as erosion, decline in soil
organic matter content, soil fertility and soil
contamination were directly or indirectly covered in
existing legislation, but only a few directives provided targets
for reducing the soil threats and supporting its ecosystem
services.

15. Thank you