Logging in central Africa: extent and impact · Gabon Congo Cameroon CAR Equatorial Guinea ... recovery Sapelli (E. cylindricum) Ayous (T. scleroxylon) 0,00 0,20 0,40 0,60 0,80 1,00

Global Change, Deforestation and the Future of African rainforests - Oxford, 4-6 January 2012

Logging in central Africa: extent and impact

S. Gourlet-Fleury, F. Baya, D. Beina, D.Y. Ouédraogo, A. Fayolle, F. Mortier, F. Bénédet, D. Closset-Kopp, G. Decocq, A. Billand


Logging in central Africa: where?

Six main countries:

404.8 106 ha

Forest area:

162.0 106 ha (40%)

Lowland rainforests:

142.2 106 ha (88% of

forested area)

Land Cover Map of Africa (GLC 2000) – DG-JRC

Data source: OFAC / COMIFAC



Rainforests area (106 ha) – Total: 162.0 106 ha

98.921.1

18.5

16.9

4.6 2.0 DRC

Gabon

Congo

Cameroon

CAR

Equatorial Guinea




Source: de Wasseige & Wala Etina, EDF 2010 (in press)

OFAC/COMIFAC

Forest area:

162.0 106 ha

Production forests:

62.0 106 ha* (38% of

forested area)

Allocated to

concessions (large):

39.0 106 ha (24% of

forested area)

* Estimated from ITTO (2011)


Logging in central Africa: what and how

much?

Contribution of the formal forestry sector to GDP: between

0.2 (Equatorial Guinea) and ≥ 6% (Cameroon, CAR)

Okoumé (Aukoumea klaineana,

Burseraceae) – 32%

Sapelli (Entandrophragma cylindricum,

Meliaceae) – 16%

Ayous (Triplochiton scleroxylon,

Malvaceae) – 11%

Azobé (Lophira alata, Ochnaceae)

Iroko (Milicia excelsa, Moraceae)

Aniégré (Aningeria sp., Sapotaceae)

Fifty commercial species, but ~10 species most valued:


Harvested timber volume (106 m3) – Total: 8.4 106 m3

98.921.1

18.5

16.9

4.6 2.0 DRC

Gabon

Congo

Cameroon

CAR

Equatorial Guinea

Rainforests area (106 ha)

Productivity:

± 17.1 m3 ha-1 AHA

(7 m3 in CAR to

45 m3 in Gabon)

0.3

3.4

1.3

2.3

0.50.5

DRC

Gabon

Congo

Cameroon

CAR

Equatorial Guinea

Total annual harvestable area (AHA): ~ 600 000 ha

Logging in central Africa: what and how

much?

2007



Logging in central Africa: how?

Management plans mandatory in all forest codes

Felling cycles: 25 to 50 years (most often 30 years)

Minimum harvesting diameters / species (Cameroon, Congo, DRC, Gabon):

most often between 60 and 90 cm dbh

Managed or under management process: 26.1 106 ha (67% of

concessions area)

3.0 106 ha FSC certified in 2008 (Cameroun, Congo, Gabon)

General problem: still limited knowledge on the mid and long-term

impacts of timber logging, and concerns about its sustainability


Settled in 1982,

110 km SW of Bangui

French government

massively investing in

forest management in

Central Africa,

needing:

Quantified data on

the effects of

logging

Better knowledge

on stands and tree

species dynamics

Assessing the impact of logging: the M’Baïki

Experimental Station


M’Baïki experimental station


Semi-deciduous

rainforest (Malvaceae,

Ulmaceae, Meliaceae,

Sapotaceae)

Mean annual rainfall:

1738 mm (1982-2007)

Large plateau (500-

600 m a.s.l.), acrisols




M’Baïki experimental station


10 plots, 9 ha each

All trees ≥ 10 cm dbh mapped and

monitored every year in the 4 ha

core zone (≥ 35 000 trees)

More than 310 tree species, mean

species density (r): 120 sp. ha-1

Three treatments implemented

between 1984 and 1987:

Control (3 plots)

Timber logging (3 plots)

Timber logging + thinning (4 plots)



Bedel & al. (1998)


Main characteristics of control plots

Commercial species (40):

22% of tree number

40% of basal area

47% of standing volume

(81% of volume ≥ 80 cm dbh)

0

50

100

150

200

250

300

350

400

10-20 20-30 30-40 40-50 50-60 60-70 70-80 >=80

Classes de diamètre (cm)

Eff

ec

tif

(/h

a)

1984

2005

0

20

40

60

80

100

120

10-20 20-30 30-40 40-50 50-60 60-70 70-80 >=80

Classes de diamètre (cm)

Vo

lum

e s

ur

pie

d (

m3

/ha

)

1984

2005


Silvicultural treatments

Treatments N

(ha-1)

G

(m2 ha-1)

V

(m3 ha-1)

% G

eliminated

Logging 4 4 66 23%

Logging + thinning 23 8.5 101 34%

Logging: ≥ 80 cm dbh

Thinning: ≥ 50 cm dbh


Impact of treatments: productivity and

recovery

Sapelli (E. cylindricum) Ayous (T. scleroxylon)

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

1984 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39

Années

Eff

ecti

f d

e sa

pel

lis

>=

80

cm d

bh

(/h

a)

Observations

Prédictions

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

Initia

l 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39

Années

Eff

ecti

f d

'ayo

us

>=

80

cm d

bh

(/h

a)

Observations

Prédictions

Logged: 1.4 t ha-1, 20.3 m3 ha-1

Volume recoverable within 30

years: 13%

Logged: 1.6 t ha-1, 28.3 m3 ha-1

Volume recoverable within 30

years: 27%


Impact of logging in Central African semi-

deciduous rainforests

Little impact at first cut:

Volume and biomass quickly recover

Little impact on floristic diversity

However, felling cycles too short (MHD too low?) to

allow commercial stock recovery

Post-logging silvicultural operations will be needed to

ensure sustainability (of the same species)


Knowledge still needed

Long-term monitoring is crucial (models need long-term data)

1980 2000 2020 2040 2060 2080 2100

0.0

0.5

1.0

1.5

2.0

Year

Num

ber

of

trees

80 c

m d

bh (

ha

1)

Plain line is the evolution predicted by a Usher matrix

model, with its 95% confidence limits in grey.

Around 200 trees are necessary to

achieve a precision of 10% to 30%

on the stock recovery rate, for an

risk of 5 to 20%

Sapelli (5.6 trees/ha) => 36 ha

Dibétou (1.3 trees/ha) => 154 ha

Sipo (0.2 trees/ha) => 1000 ha !!!

Too large areas needed can be partly

compensated by a greater number of re-

measurements (Picard & Gourlet-Fleury, 2008)

Sapelli (Picard & al., 2008)



Spatial network of plots aiming at dissociating logging and

environmental effects is crucial => DynAfFor project

M’Baïki

Yoko/Biaro

Couples of 400 ha plots,

combined with 9 ha plots

One control / one logged

after 4 years

(At least) four other sites

needed to complete the

DynAfFor network …

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11 12

Mois

To

tal d

es

pré

cip

ita

tio

ns

(m

m)

LISALA

BUTA

OUESSO

IMPFONDO

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11 12

Mois

To

tal p

réc

ipit

ati

on

s (

mm

)

PORT FRANCQUI



Better knowledge of ecological requirements and history of

vegetation and disturbance is crucial => CoForChange project

23 forest concessions

Around 6 millions ha of

management inventories

Multi-disciplinary study of the

determinants of spatio-

temporal tree species

distribution

Logging in central Africa: extent and impact · Gabon Congo Cameroon CAR Equatorial Guinea ... recovery Sapelli (E. cylindricum) Ayous (T. scleroxylon) 0,00 0,20 0,40 0,60 0,80 1,00

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