Download Incorporating ecological process in landscape-scale planning

Incorporating ecological process
in landscape-scale planning
Dave Hole
Why target ecological processes?
 In the past conservation planners have focused on
PATTERN – e.g. representation and retention
 To ensure persistence MUST incorporate PROCESS
 If lost, difficult to restore – therefore apply precautionary
approach and target as a matter of urgency
Incorporating ecological processes
 Few attempts made – but see CFR and SK in South
Africa; WWF in Central Indochina Dry Forests Ecoregion
 Why so few? – two major challenges:
1. Identification of critical processes
2. Defining spatial/quantifiable targets
 Generic criteria – e.g. conserve large areas = probably
capture many processes, but all?
First things first – what actually is an
ecological process?
 Biotic interactions, abiotic processes and ecosystem
services all classed as ‘ecological processes’
 Working definition? – “flows of nutrients, water,
energy, organisms, and other resources between
landscape elements” – HUGE number of potential
processes
Continued…
 How do we narrow down to those that are:
1) Critical for the persistence of GT/GC species/KBAs
2) Can only be conserved at the landscape-scale
 Several considerations:
1) Different ecosystems are structured by just a few
dominant processes (?)
2) Many will continue to function at site-scale
3) Many probably not manageable
First-cut – critical ecological processes
Category
1) Species driven processes
Interspecific ecological interactions
Intraspecific population dynamics
Disturbance regimes
2) Non-species driven processes
Disturbance regimes
Resource flows
Other
Process
Predation*
Herbivory*
Competition
Seed-dispersal*
Pollination*
Parasitism
Migration and dispersal
Metapopulation dynamics
Source-sink dynamics
Engineer species*
Grazing/trampling*
Fire*
Flood*
Other*
Hydrology
Nutrient-cycling
Evolutionary processes
1) Species-driven processes:
Interspecific ecological interactions
 E.g. predation, herbivory, pollination
 Operate over a wide-range of spatial scales
 Loss of (e.g. top predators) = extinction cascade
 ‘Keystone’ species
 Identify keystones that cannot be conserved at site-scale
a) Predation and herbivory
X
 Many interactions conserved at site-scale
 GT/GC species, keystone role, cannot be conserved at
site-scale = picked up at species definitions stage
 Keystone role, cannot be conserved at site-scale, but
non-threatened, e.g.
1) Impact on prey/flora vital for persistence of
globally threatened species/KBAs
2) Represent a crucial prey-base
X


a) Predation and herbivory – continued…
 Examples:
1) Sea otters influence persistence of kelp forests
through predation of sea urchins
X
a) Predation and herbivory – continued…
 Examples:
2) Wolves regulate moose populations, preventing
overbrowsing of riparian willow communities,
maintaining neotropical migrant bird diversity

3) Anadromous fish are critical prey-base for a wide
range of predators

b) Pollination & seed-dispersal
 Crucial in spatial dynamics, regulating community
stability and persistence
 Middle of global pollination crisis; >180 vertebrate
pollinators listed as endangered
 Diversity of pollinators/seed-dispersers = processes
occur at a range of spatial scales
b) Pollination & seed-dispersal – continued…
X
 Many interactions conserved at site-scale
 GT/GC species, keystone role, cannot be conserved at
site-scale = picked up at species definitions stage
 Keystone role, cannot be conserved at site-scale, but
non-threatened, e.g.
1) Pollinators/seed dispersers of huge range of
plants (e.g. Flying foxes, hornbills)
2) Pollinators/seed-dispersers of keystone plant
resources (e.g. fig-wasps)
X


b) Pollination & seed-dispersal – continued…
 Examples:
1) Lesser long-nosed bat [VU] in
N. American deserts pollinates
X
Agave and columnar cacti
2) Pteropus spp. on oceanic
islands and in mangrove
ecosystems

b) Pollination & seed-dispersal – continued…
 Examples:
3) Figs and their fig-wasp pollinators

b) Pollination & seed-dispersal
– continued…
 Examples:
1) Southern cassowary [VU]
in Australia – sole
disperser of > 75
rainforest plant species
X
2) Hornbills (Ceratogymna spp.)
in Cameroon – disperse 22%
of known tree flora

b) Pollination & seed-dispersal
– continued…
 Examples:
3) Pteropus spp. in Samoa –
utilize fruit resources
of > 69 plants spp. from
51 genera in 36 families

c) Species-driven disturbance regimes –
e.g. engineer species; grazing/trampling
 Engineer species significantly modify their
environments (e.g. pocket gopher, termite)
 Grazing/trampling by large herbivores represents
a significant large-scale disturbance process
 Some species may be non-threatened but
still require conservation above the site-scale
c) Species-driven disturbance regimes –
continued…
 Examples:
1) Asian elephants [EN] in Indochina dry forests –
influence forest structure and plant community
composition through selective grazing
X
d) Species-driven disturbance regimes –
continued…
 Examples:
2) Beavers in N. America – dramatically alter riparian
landscapes

3) White rhino in southern Africa – prime controlling
influence on tree-shrub-grass balance in savanna
ecoregion

2) Non-species-driven (abiotic) disturbance
regimes
 Occur in all biomes, helping to shape ecosystems
 Often modified by humans, but crucial for
persistence of individual species and ecoregions
 Vast range of spatial scales – e.g. tree-fall (local);
hurricane (regional); El Nino (continental)
 Some will require conservation at the landscape-scale
a) Fire regimes
 Anthropogenic fire disturbance is widespread
 Remains a crucial natural disturbance – e.g. grasslands
 Many fire regimes maintained at site-scale
 Where large areas are disturbed (e.g. savanna
systems) – requires landscape-scale conservation
a) Fire regimes – continued…
 Fire periodically affects most ecoregions – but
several are strongly dependent for their persistence:
1) Fynbos ecoregion (South Africa) – determines
protea demography and successional sequence
a) Fire regimes – continued…
2) Prairies (North America) – selects against woody
plants, favoring fire-adapted grasses and forbs
3) Cerrado (Brazil) – maintains dynamic balance
between savanna and forest ecoregions
b) Flood regimes
 Flood disturbance crucial
to persistence of a variety
of globally threatened
species and/or ecoregions:
1) Flooded forests (Brazil)
– flood pulse regulates
forest structure, species
richness and distribution
b) Flood regimes – continued…
2) Pantanal (Brazil) – maintains
habitats and dictates
abundance and availability
of fish-prey
c) Other disturbance regimes
 Many other disturbance processes exist – e.g. tree-fall,
wind, landslides, El Nino events, drought
 Some likely to be conserved at the site-scale e.g.
(tree-fall)
 Others not practicable to manage (e.g. hurricanes) – but
manage for impacts on GT/GC spp
Targeting and managing critical ecological
processes
 Processes are complex and often poorly understood
 For species-driven processes = identify & target
keystones that cannot be conserved at site-scale alone
 GT/GC keystones picked up at species outcomes
 Need to identify and target non-threatened keystones
– maintain EFDs
 Degree of redundancy may help?
 Target/monitor trophic guilds? (e.g. seed dispersers)
 But careful of ‘wild goose chase’
Targeting and managing critical ecological
processes – continued…
 For non-species-driven processes:
 Some we can/should manage – e.g. fire, flood
 Others we cannot – e.g. volcanoes, hurricanes
 Need to consider Minimum Dynamic Area
 Non-interventionist – target Natural Range of Variability
 Interventionist – mimic impacts required for target species
 Decision may depend on whether a wilderness area or
a hotspot
To think about
 Do we target all critical processes in every landscape/
seascape (i.e. precautionary approach) or only those
where a direct link to GT/GC species or KBA persistence
is proved?
 Further research clearly vital (e.g. identify
non-threatened keystones AND provide evidence of role)
 Other processes (e.g. hydrology; nutrient cycling;
evolutionary processes) still need to be evaluated