Transcript PPT - Forest Genetic Resources Training Guide

Trees outside of forests
Conservation of tree species
diversity in cocoa agroforests
in Nigeria
David Boshier
What are the impacts of human
interventions on trees?
What are the genetic impacts of
human interventions on trees?
Examples from other classes
impacts of human interventions on trees?
fragmentation, afforestation, silviculture,
deforestation, agriculture, shifting cultivation,
premature death, clear fell
genetic impacts of human interventions on trees?
hybridisation, inbreeding depression, dysgenic
selection, loss of genetic diversity, species loss,
increase variance between populations, genetic
loss/erosion
Genetic impacts of human
interventions on trees
Humans impact forests in a variety of ways, eg
• conversion of forest to agriculture & other uses
• forest fragmentation
• logging, harvesting of different types
• domestication/breeding
Need to consider influence of interventions on
functionality of tree populations & relevance to
conservation
Genetic impacts of human
interventions on trees
All interventions influence genetic diversity of trees
to greater or lesser extent
In many circumstances impacts on genetic diversity
may not be a priority
Foresters/conservation managers need to be able
to identify • how patterns of genetic variation are altered
• under what sort of circumstances genetic diversity
and its loss may become limiting
Where & how should we conserve?
In situ - Ex situ
In situ - reserve system of undisturbed,
protected areas within natural distribution
(ecosystem based)
Ex situ - artificial maintenance of populations
outside natural distribution (species based)
Impacts of human disturbance
not random
• often
superimposed on
habitat
heterogeneity
• may lose species
and populations
adapted to
lowlands/good
soils
Conservation of biodiversity in
situ: trees as a paradigm
ideal reserve model
emphasis: large, continuous, protected areas
limitations: location, size, security, biology:
–
–
–
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movement of animals
extensive distribution of many species
gene flow between populations
upland, non agricultural areas
essential but not sufficient
Where should we conserve?
In situ - Ex situ
In situ - reserve system of undisturbed,
protected areas within natural distribution
(ecosystem based)
Ex situ - artificial maintenance of populations
outside natural distribution (species based)
Conservation of biodiversity ex situ:
methods and limitations
seed banks - problems of regeneration
plantations - changes in gene frequencies, few
populations
botanical gardens - deficiencies for gene pool
conservation
© RBG Kew
© RBG Kew
© DH Boshier
a large number of individuals of many species have
long ago ceased being ecologically (and
evolutionarily) reproductive; they flower but set no
These
are the
deadnever lead to
seed, or if they
set seed,
theliving
seedlings
Janzen 1986
recruitment of adults.
© DH Boshier
Issues of concern – conservation
of tree genetic resource outside of
forests
Conservation of species and genotypes
Conservation paradigms – in situ, ex situ, through
use on farms – circa situm
The ‘Living Dead’ or
an ally for conservation?
Location of Nigeria
Lovoa trichilioides
Milicia excelsa
45 tree species in 21ha
agroforests – 6 species with
IUCN classification
Lophira alata
Gossweilerodendron balsamiferum
Endangered - IUCN
Vulnerable - IUCN
Biodiversity and bioquality
number of species or the proportion of rare
species?
Use the information given here to either:
a) derive an action plan to ensure optimum conservation
benefits in terms of tree species diversity in the cacao
agroforests of Nigeria, or
b) present a case for the conservation benefits in terms of
tree species diversity in the cacao agroforests of
Nigeria