Post on 24-Dec-2015
transcript
Trees outside of forests
Conservation of tree species diversity in cocoa agroforests in NigeriaDavid Boshier
What are the impacts of human interventions on trees?
What are the genetic impacts of human interventions on trees?
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
Examples from other classes
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 - reserve system of undisturbed, protected areas within natural distribution (ecosystem based)
Ex situ - artificial maintenance of populations outside natural distribution (species based)
In situ - Ex situ
Impacts of human disturbance
• often superimposed on habitat heterogeneity
• may lose species and populations adapted to lowlands/good soils
not random
Conservation of biodiversity in situ: trees as a paradigm
ideal reserve model
emphasis: large, continuous, protected areas
limitations: location, size, security, biology:– 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 - reserve system of undisturbed, protected areas within natural distribution (ecosystem based)
Ex situ - artificial maintenance of populations outside natural distribution (species based)
In situ - Ex situ
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
a large number of individuals of many species have long ago ceased being ecologically (and evolutionarily) reproductive; they flower but set no seed, or if they set seed, the seedlings never lead to recruitment of adults.
© DH Boshier
© DH Boshier
These are the living deadJanzen 1986
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
Can valuable tree re
sources persist
outside of forests and if
so what
measures need to be ta
ken to
ensure they persist?
an ally for conservation?
Up to 140 species of b
irds & 40 tre
e species
New tree species discovered in cafetales
Location of Nigeria
Farmer F
ield S
chools
Lovoa trichilioides
Milicia excelsa
Lophira alata Vulnerable - IUCN
Gossweilerodendron balsamiferum Endangered - IUCN
45 tree species in 21ha agroforests – 6 species with IUCN classification
But, 62 species in 0.56 ha of primary
forest - 14 species with IUCN
classification
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