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