rehabilitating the biodiversity and productivity of moist forests
TRANSCRIPT
Rehabilitating the biodiversity and productivity of moist forests and deciduous
woodlands through active resource use
Coert J. GeldenhuysForest and Wood Science, Stellenbosch University, Stellenbosch
Plant and Soil Sciences, University of Pretoria, Pretoria
Capacity-development workshop for Central, Eastern and Southern Africa on the restoration of forests and other ecosystems to support the achievement of the AichiBiodiversity Targets, 2-6 October 2017,
Durban, South Africa
What would be your thoughts about these situations?
Timber harvesting
Fire
Charcoal production
Slash & burn Plant invasions
PowerlinesRoad construction Mining
Bark harvesting
Residences
Is human resource use always bad?
Or is conservation always good?
What criteria do we use for objective assessment?
I suggest that we have many wrong perceptions:
Consider that:
What looks good may be ecologically bad;
Or, what looks bad may be ecologically very good!
Every time I ask myself: Is this OK or bad?
If it is BAD, how bad? Why?
How does this relate to natural processes?
Can it be restored?
• Uncontrolled resource use beyond recovery potential of targeted species?– Timber products - large-dimensions– Non-timber forest products – poles, fuel wood (charcoal & firewood),
wood carving, etc– Non-wood forest products – bark for fiber and/or traditional medicine
• Changed fire regimes in fire-prone systems?– Exclusion of fire– Cooler fires
• Alien plant invasions?– Light-demanding versus shade-tolerant species
• Forest/woodland cleared for alternative uses?– Crop cultivation - Food, bio-energy products, timber plantations, etc– Development of settlements, urban development, infrastructure,
mining, etc
What are the causes of forest/woodland degradation?
• Major global concerns underlying need for cost-effective approaches to rehabilitate natural forests/woodlands
– Degraded and cleared through • slash-and-burn traditional agriculture• charcoal production• uncontrolled timber-harvesting practices with no silvicultural
management• clearing for commercial agriculture, plantation forestry,
infrastructure development and mining
– Alien plant invasions threaten biodiversity & ecological processes of natural vegetation systems, including natural forests
– Climate change, Green-house gas emissions, etc
Why do we want to restore the specific landscape, ecosystem, species?
• Restore essential ecological processes– Basis for maintaining optimum biological diversity– Adaptations to imposed stresses, disturbances, etc
• Restore their biological diversity per se– Many floral and faunal components depend on forest ecosystem– Cannot be done without considering ecological processes at different
levels
• Restore productive capacity– for diverse resource use options of diverse resource users
for diverse forest products
• Restore their environmental services– nutrient cycling, carbon sequestration, soil and water conservation, etc
• Combination of ALL = Basic good forest management
Why do we want to restore the specific landscape, ecosystem, species?
When is a forest in degradation or in recovery?
FORESTS have INTEGRAL NATURAL DISTURBANCE & RECOVERY PROCESSES
on the outside
on the inside
Lightning without fire Lightning with fire Windfall gaps
Disturbances a natural part of all vegetation formations• Biological components (species) of all forest/woodland types
- represent adaptations to different disturbance regimes- form part of different (recovery) stages of vegetation- they show different
• Growth/Life forms: trees, shrubs, herbs, etc.• Bark types; Fruit & seed types • Relative tolerances of forest/woodland species to
• Shade (pioneer vs early regrowth vs mature forest)• Browsers (fire, fauna, people)
A disturbance is …..• A discrete event (fire, browsing, tree fall,..) changing
- species & structure
- physiological processes
- resources: ± light, oC, nutrients
• Called a - Non-event – frequency/impact too minor to cause response- Incorporated – within adaptation & tolerance limits of entity; necessary
to maintain entity in current state- Disaster – changes entity into new state; increases fitness
- Entity level: individual, population, community or landscape
• Human activities need to simulate natural disturbances to which the forest/woodland system & its components are adapted• Keep human resource use disturbances to level of Non-event &
Incorporated disturbance at level of population & community• Focus rehabilitation at level of disaster to population, community, ...
Disturbances a natural part of all vegetation formations
• Total biodiversity of a particular vegetation system- Depends on maintenance of different natural disturbance-recovery
processes in that vegetation
- If we totally protect a system, we loose important biodiversity components of the system
• Action of disaster to one level may benefit- Another level
• Eg breakdown of community structure (disaster) may benefit population of pioneer/early regrowth species (eg Prunus)
- Another component at same level
• Eg lack of regeneration of pioneer species (disaster) may benefit regeneration of more shade-tolerant species
• Greater disaster of disturbance at one level- Longer period of recovery of that component/level towards original
condition of forest/woodland prior to disturbance event
Diversity in adaptations to disturbance• Each forest has species adapted to different disturbance factors
at different regimes, mainly- Shade tolerance in closed evergreen forests
- Fire tolerance in deciduous woodlands
- Other secondary factors = primary factors in some species
• Each species functions best under optimum conditions related to primary factor of adaptation, in terms of - Regeneration, establishment & productive growth
- = Main ecological criteria for sustainable functioning!
• Species dominance changes from early regrowth stands towards mature forest - In which stage do our target species show optimum development &
growth?
- What would be the best approach to rehabilitate specific species/systems
A disturbance …
• may vary in its effect or impact, depending on - its regime (intensity, frequency or area of impact)- component species of system & their adaptations
• regime x habitat/site = landscape patterns= Vegetation types & Biodiversity patterns
• forest-woodland-shrubland-grassland in same area
Forest/woodland formations in Africa
And how do they determine the composition & dynamics of the different systems, resource use practices, rehabilitation actions?
Everything we do causes changes – even doing nothing!
• Forest/Woodlands not museum pieces – DYNAMIC SYSTEMS!!
• How should we deal with Disturbance-Recovery processes in the forest/woodland environment?• Is it the inability of the vegetation to respond?
• OR is it our poor understanding [despite good intentions] of natural forest & woodland dynamics?
• What multiple-use management systems will maintain natural diversity when we use forest products & services?
• Can we rehabilitate natural complexities (species x age) in degraded forests/woodlands?
Detailed forest location pattern with fire pathways: Storms River
Sto
rms R
ive
r
bri
dge
Solid = fire burn, thickness = severity Broken = fire jump, up to 4 km
1 2
Plantations planted in fire pathway…. & regularly destroyed!
FOREST LOCATION PATTERN & PROCESS:
Forest location pattern determined by fires driven by prevailing winds (Bergwinds) in dry season:
Forests persist in ‘fire-shadow’ areas in landscape
In South Africa, natural forests occur in areas with rainfall >725 mm/a in summer rainfall & >500 mm/a in winter/all year rainfall7% of RSA has rainfall >800 mm/a; Forests cover only 0.1%Similar patterns can be seen in other parts of AfricaRehabilitating natural forest in the fire pathway will be fatal
• Fast-growing pioneer trees – often invasive alien species (eg Wattle)
• Buffer/nurse more variable & extreme conditions of regularly disturbed grassland, shrubland & agricultural fields
• Facilitate establishment of shade-tolerant forest species
• Typical forest succession process
Stage 1: Stage 2: Stage 3: Stage 4:Dense pioneer stand Growing up & Further development/ Pioneer stand totally
self-thinning thinning removedNo understorey Sparse understorey Young regrowth forest Mixed regrowth forest
Invader plant, or Invader plant or planted Forest trees and otherPlanted tree for woodlot tree removed species establishingtimber, fruit, etc. for use or other purpose naturally or interplanted
(thinning) (potentially traditionallyused species)
Alien clearing action
Rehabilitation action
AND we can manage the process, or benefit from it, at low cost!
Woody plants establish in landscape
with disturbance (fire) exclusion
Pines
Same happens with plantation stands on forest margin!
AND with INVADER PLANT stands!!
EucalyptsAcacias
Keurboom (Virgilia divaricata) after fire
Our CONCEPT: Recovery of natural forest species follows a natural succession process towards diverse systems
2. Not Natural-Forest Environment
- in fire zones
2.2 Non-forest, fire-
adapted vegetation: Grassland, Shrubland,
etc
Follow traditional
IAP clearing methods: cutting,
herbicides, burning, etc
Follow stand manipulation process as for natural forest environment
(a) Development stage 1
1.1 Stands have NO utilization potential
Decision tree to decide on action in Invader plant stands in area with natural forest
1. Natural Forest Environment
- in fire-shadow areas
Follow relevant stand manipulation guidelines
for each stage to facilitate natural forest recovery
2.1 Naturalising
Natural Forest:Area became
non-fire landscape (in
timber plantations or urban areas)
3. C
on
vers
ion
to
pro
du
ctiv
e co
mm
erc
ial
lan
d u
se
(cro
pp
ing,
gr
azin
g, t
imb
er
pla
nta
tio
n, e
tc)
Focus on integrated, cost-effective use of poles,
timber, etc. & good forest recovery;
Minimize damage to existing regeneration; if
necessary, allow invasives to establish after cutting stand & manage recovery via
stages 1 to 3
1.2 Stands have utilization potential
(b) Development stages 2 & 3
(c) Development stage 4
Undisturbed forest
Disturbed forest in different stages of recovery: Gabon
Recovery is fast – by pioneer & early regrowth species – No need to plant mature forest species at high costs!
Slash & burn recovery in Tropical Moist Forest
Okoume 40 years after slash-&-burn
Sep 2013
Aug 2015Pri
nci
pe
Isla
nd
: Tre
ma
ori
enta
lisre
cove
ry 2
ye
ars
afte
r a
fire
Limba (Terminalia superba): 80 cm DBH left, 50 cm DBH right - in Slash & Burn site after 50 years (Cameroon)
Left: Okoume (Aucoumea klaineana) killed on edge of Slash & Burn site, Gabon – no value for farmer. Right:
Okoume stand of 40 years developed from pioneer stand with Parasolier (Musanga cecropioides). Selective
thinning of Okoume stands could be done by local farmers for benefits & forest recovery!
Examples from Cameroon, Gabon & Principe
Iroko / Amoreira (Melicia excelsa) a fast-growing pioneer tree in many parts of Africa and Sao Tome & Principe islands. Fastest-growing trees of 80 recorded trees grew >5 cm DBH per year
Natural Pioneer & Alien plantation/invader species can be your PARTNER in forest rehabilitation & biodiversity
recovery!• Use natural Pioneer/Alien process to reduce costs:
• provide rapid ground cover - prevent erosion
• add litter to degraded site - restore nutrient cycling
• provide shade to facilitate establishment of shade-tolerant natural forest species – improve biodiversity recovery, no planting
• can provide rural resource use needs (fuel wood, poles, construction material) - reduce pressure on natural forest; thinning
Stage 2 Stage 3 Stage 4Stage 1
We need a changed mindset towards this cost-effective way to rehabilitate natural forest!
Miombo woodlands as main ecological systemMiombo Eco-region
• Seasonally dry with long dry season (4-6 months), with fires
• Adaptations to Browsing (fire, animals, people) as main disturbance factor
• Inherent low soil fertility
• Most tree species are light-demanding = develop even-aged stands
Dry (light green) & Wet (dark green) MiomboMozambique, Zimbabwe, South Africa (?), Malawi, Zambia, Angola, DR Congo, TanzaniaDominated by 3 genera: Brachystegia, Julbernadia, Isoberlinia
Closed woodland (forest) ↔ open woodland ↔ wooded grassland ↔ bushland & thicket = could be stand recovery stages
SUBSISTENCE:
• Daily domestic consumptive use
- Most rural, poor people
- From immediate vicinity of village
COMMERCIAL:
• Small, micro & medium enterprises (SMME’s)
- Fewer individuals, families & some communities
- Use resources & entrepreneurial skills
- Earn income beyond daily livelihood needs
• Industries, mainly export markets (using natural areas)
- Use specialized skills, technology & investment
- Timber industries (for construction, furniture and plywood)
• Conversion of woodlands
- Crops (agriculture + tobacco, timber plantations),
livestock, infrastructure
• Conservation & Nature-based tourism (Parks)
Diverse products, values & services from woodlands
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Population pressure & Livelihood needs
• Commercial ventures over large areas– Agriculture, forestry, mining, parks, urbanization, REDD+, etc
• Exploit resources for economic development elsewhere
• Reduce rural livelihood options– Increase pressure on resources
Crops
Perception that this is
area of Village
But Village area is
much larger
Land for commercial
land uses
superimposed on
Village areas – with
severe consequences
Main direction of perceived degradation in Miombowoodland structure:
Open/closed mature woodland to scrub woodland
Main factors in perceived degradation of woodland:
Clearing for growing crops; Collecting construction poles of different size;
Collecting fuel wood (firewood & charcoal) for energy (cooking, etc)
HOWEVER, change is not in one direction, but cyclical: also from scrub woodland to open/closed mature woodland
Traditional landscape: • Integrated agriculture, forestry,
settlements & conservation• Maintain ecological processes,
diversity & productivity
Agriculture
ConservationMining
Forestry
Commercial landscape: • Segregated agriculture, forestry,
mining, urbanization & conservation• Degrade ecological processes,
diversity & environmental health
What, and whose, criteria do we use to judge degradation & deforestation?
Government policies favor large-scale commercial ventures
Many negative perceptions on Secondary forests, Slash & burn agriculture, Charcoal production, Clearing for crops - BUT, basis of livelihoods of millions
Browsing by fire, wildlife & people:Main disturbance in Miombo woodland
Miombo species persist through vegetative regrowth from rootstocks & cut stems
Sprouting from rootstocks &
damaged stems:
Main regeneration system in Miombo
woodland
• Essential to clear mature Miombo (not degradation or deforestation):• Vegetative regrowth
needs light to grow fast• Develop even-aged
stands with trees of uniform size
• Most diverse & productive
Slash-&-burn traditional agriculture & charcoal production
Cyclic clearing-cropping-fallow-regrowth maintains Miombo biodiversity & productivity
Moribund, old-growth stand & old, stunted
seedlings on rootstock = 1 to >10 yrs old
Active regrowth stand, even-aged, after slash-
&-burn agriculture = 10 yrs old
• Extensive areas of secondary Miombo woodland:o Light-demanding species growing fast from vegetative regrowth on
rootstocks/stumps to form even-aged standso = basis for sustainable resource use
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Mature woodland
Advanced regrowthAdvanced regrowth
Young regrowth
Earlier cleared
Recently cleared and waiting to be burnt
Cyclic clearing = fast recovery of Miombo woodland:= NOT unidirectional loss
Very healthy, biodiverse & productive woodland: provide wide range of pole sizes, firewood, fiber & other uses for rural livelihoods
Regular disturbance maintains plant species diversity: Most woodland species present from start of Miombo regrowth after Slash & Burn and Charcoal Production & persist on site (rootstocks)
Land use Total species
recorded (woody &
herbaceous
Undisturbed woodland 50
Timber harvesting 64
Slash & burn agriculture 69
Charcoal production 74
What looks good (undisturbed woodland) = not necessarily ecologically goodWhat looks bad (regular stand replacement) = ecologically good to rejuvenate
Miombo woodland & species (best silviculture)
With perception of good or bad
Zambian study: Syampungani, S., Geldenhuys, C.J. & Chirwa, P.W. (2016). Regeneration dynamics of Miombowoodland in response to different anthropogenic disturbances: forest charaterisation for sustainable management.
Agroforestry Systems
7yrs old regrowth stand
Woodland stands in development stages are even-aged: need stands in each age class for sustainable use
10 cm diameter in 7 years = 1.4 cm/yr in stem diameter growth: With NO silvicultural management
Regrowth is fast in secondary Miombo woodland
10 yr old regrowth stand
Can we improve stand growth
through silvicultural
management?
30 yr old regrowth stand
32
Silvicultural management in stand development stages= key to better resource use management:
Selective thinning can provide laths THEN poles THEN timber
Stage 11–2m ht
Stage 35–15m ht
Stage 22–5m ht
Stage 4 (mature)12–25m ht
Selective thinning & pruning as part of normal harvesting of poles, firewood & fibers: women in stages 1-2, men in stage 3
Clearfell in groups (gaps): timber, charcoal & cropping33
Implement selective stem thinning and branch pruning:Remove poor stems: form, defects, suppressed, etc;
Provide growing space for good stems; Use material for poles of different sizeAnnual resource use come from all development stages
to provide in pole & smaller dimension fuel wood needs; to improve growth of selected remaining stems
(free use of sunlight, carbon dioxide in atmosphere; moisture & nutrients in soil)34
Real example Plot 1 Plot 2 Plot 3
Branches removed 90 93 101
Poles removed 41 81 97
Poles of better quality left behind standing 80 112 120
Selective thinning & pruning of trees:Active farmer training: Cut branches & poles from 20m x 20m plot
Initial effects of thinning & pruning on residual standsSt
age
1 M
ulo
mb
a
0% 50%100%
Observation plots = 0.04 ha (20m x 20m)
Stag
e 2
Cat
abu
a 0% 50% 100%
Stag
e 3
Lib
un
i 50% 100%0%
Catabua stage 2Catabua stage 2 Aug 2014
Response to 30% & 100% cut after 1 year
30% thinning 100% cut
Chinvano stage 2
Chinvano stage 2 Chinvano stage 2 Chividzi stage 3
Mulomba stage 1/2
100% cut
This is not deforestation: all species present in system: sprout from dormant rootstocksDegradation is only in terms of stand structure; not in terms of plant diversityRegrowth is productive: many cut plant sprouts grow to >1 m height in 1 yearStems require light for active regrowth & only cut stems respond vigorously
Strong demand for light to grow – on edge!
Natural woodland cover
Nat
ura
l wo
od
lan
d b
iod
ive
rsit
yHigh
High
Low
Low
Commercial Agriculture
All woodland development
stages
Protected areas
Traditional production systems:
S&B agriculture & Charcoal
SMME’s in integrated, land
management systems
Commercial Forestry
Conceptual framework for Sustainable development of resources within woodlands
Carbon stocks
Car
bo
n s
eq
ue
stra
tio
n r
ate
s
Soil fertility
Soil
fert
ility
re
cove
ry
Small-scale farmer maintaining mosaic of woodland stages Regular use of products of different dimensions from different
farmer-selected stands as part of silvicultural management
Stage 0
Stage 2early
Stage 2late Stage 3
earlyStage 3
late Stage 4
Cut
Stage 1
Prune Thin
Productive use of secondary Miombo woodland while maintaining biodiversity & ecological processes
Integrated management of Timber concessions Combining harvesting of quality timber, charcoal production, slash-
and-burn agriculture & other uses from woodlandStep 1: Cut quality timber
Step 2: Charcoal from other trees – in larger gap
Step 4: Facilitate tree regeneration in gap
Gap diameter = 3-5x canopy height
Step 3: Slash & Burn cropping in gap
Develop CONTROLLED sustainable resource use in development zones around national parks and reserves
to maintain maximum diversity
Zonation of National Parks by Biosphere reserve conceptIntegrating environmental services, ecological processes & use value• Core area: Unique habitats,
sensitive sites, special ecological or cultural interest, etc– Minimum interference in system
• Buffer zone (around core area): Structure/function of natural system not disturbed/changed– Low-density – high quality
ecotourism, minimum interference– Minimum resource use, in tune with
natural ecological processes
• Transitional or development zone: Village areas with controlled traditional resource use practices– Controlled resource use with
moderate disturbance in tune with ecological processes
– Facility & craft development for ecotourism (eg lodge structures & curios)
Integrated land use management at landscape scale will maintain woodland diversity, productivity and ecological processes, for both plants and animals,
at different levels: farms, villages & districts
Reduce areas of commercial forestry and agriculture, and manage these as out-grower schemes with rural farmers.
Maintain woodland corridors within intermediate –large-scale crop agriculture & forestry
We need changed mindsets to adopt integrated, multiple-use & cost-effective approaches towards recovery of forest &
woodland systemsTo maintain natural woodland biodiversity & productivity
To ensure productive & cost-effective supply of products, values & services; including to sequester carbon at faster rates!
Thanks for your interest & attention
• System a better option than REDD+ (climate mitigation action)- No extra costs to farmer (regular resource use in development stages)
- Farmer remains on land
- Not confined to REDD+ project area & project period
- REDD+ can be aligned with it (high rate of carbon sequestration)