WHAT ROLE FOR MARINE PROTECTED AREAS IN A
Canary Rockfish (Sebastes pinniger). Photo by Brian Klinkenberg.
Climate change threatens the ability of marine protected
areas to deliver intended biodiversity and resource conservation outcomes. In
light of this, should governments and stakeholders pursue their creation? This
paper reviews the implications of climate change for marine ecosystems and
suggests that marine protected areas can serve several important conservation
functions in spite of climatic change. The paper also outlines recommendations
for marine protected area design and management that will mitigate detrimental
effects of climate change on the efficacy of marine protected areas. Recommendations
are based on three central themes that should guide marine protected area
design and management: acknowledging uncertainty, adopting a precautionary
approach, and implementing adaptive management.
“Decisions about the siting and design
of reserves and assumptions about how much management will be needed in the
future must reflect the increased demands, both economic and biological, of
global warming.” (Peters and Darling
Marine ecosystems are
extremely valuable, providing an irreplaceable array of essential ecosystem
goods and services worth over $20 trillion, or 63% of the global total
(Costanza et al. 1997). They are also subject to anthropogenic stressors such
as overfishing and habitat degradation that have resulted in large-scale
changes to their composition and function (Dayton et al. 1995; Pauly et al.
1998; Jackson et al. 2001; Myers and Worm 2003; Pandolfi et al. 2003). Marine
protected areas (MPAs) have been promoted as a key tool that can mitigate these
threats by conserving marine biodiversity and facilitating more sustainable
fisheries management. The implementation of MPAs around the world is growing
quickly; indeed, the 2002 World Summit on Sustainable Development called for a
global network of MPAs by 2012 (Sherman 2006).
has documented numerous outcomes of spatial protection for marine areas,
including higher organism density, biomass, species diversity, and numbers of
large organisms than in adjacent areas (Russ and Alcala 1996a; Murawski et al.
2000; Roberts et al. 2001; Halpern 2003). They can also function as refugia
from the genetic or selection changes imposed by fisheries and provide a buffer
against the consequences of management errors and stochastic events (Allison et
al. 1998; Murray et al. 1999; Pauly et al. 2002; Lubchenco et al. 2003). With
respect to fisheries management, these functions can decrease the chance of
stock collapse, accelerate population recovery rates, decrease variability in
annual catches, provide fishery independent data, and prevent habitat
destruction associated with destructive fishing practices (Murray et al. 1999).
These conservation benefits can be accompanied by the spillover of fish into
adjacent areas and the export of eggs and larvae (Bohnsack 1993; Russ and
Alcala 1996b; Roberts et al. 2001; Gell and Roberts 2003). Ecological modeling
suggests that MPAs can even be useful for highly mobile species such as cod in
reducing the risk of fishing overexploitation (Guenette and Pitcher 1999).
The ability of MPAs
to deliver these outcomes may be threatened by anthropogenically-driven global
climate change. Atmospheric concentrations of carbon dioxide (CO2)
have risen 31% above average pre-industrial levels within this millenium. Sea
levels have risen an average of 1-2 mm per year in the 20th century
due primarily to the thermal expansion of seawater and freshwater runoff from
glacial melt (IPCC 2001). CO2 levels are expected to rise another
50-250% by 2100, with sea levels rising as much as 1 m (IPCC 2001). Global mean
surface temperatures will likely rise by 1.4-5.8°C in the next 100 years, a
rate without precedent in the last 10 000 years that will cause further ocean
warming (IPCC 2001). Climate change has already triggered significant change in
the earth’s physical systems and biogeochemical cycles, with more dramatic
change expected in the near future. These changes will in turn dramatically
alter the distribution and abundance of species and reconfigure the composition
and function of marine ecosystems (Harley et al. 2006; Lovejoy 2006). Thus, the
features represented in marine areas set aside for protection may shift or
disappear over time. This raises important questions about spatially static
protective measures like MPAs, which are the basis for this paper: are MPAs a
rational long-term marine conservation tool given that climate change will
alter marine ecosystems? If so, how should our understanding of climate change
affect the planning and management of existing and future MPAs? Examining these
questions is paramount for determining the most viable means of marine
conservation for the future. Questions about protected areas in the context of
climate change have only begun to be seriously addressed, and even then only on
land, despite the recommendation of Peters and Darling over 20 years ago
(Peters and Darling 1985; Halpin 1997; Suffling and Scott 2002).
Sea Otter (Enhydra lutris). Photo by Brian Klinkenberg
To examine these
questions, this paper reviews relevant academic literature to determine if and
how MPAs can be effective long-term conservation tools. First, I describe
salient features of marine environments in comparison to terrestrial
environments to highlight how and why climate change will affect oceans in
unique ways. This comparison will also make clear how MPAs have a different set
of challenges than terrestrial protected areas which preclude the direct
transference of terrestrial protection strategies to the marine environment
(Allison et al. 1998). Next, I summarise the potential effects of climate
change on abiotic ocean processes and resultant possible effects on marine
biotic communities, focusing on coastal marine ecosystems. The paper then
examines whether MPAs have a long-term conservation role to play and considers
strategies for making MPAs more effective in the face of climate change. To
inform the latter stages of the paper, I draw from literature on biodiversity
and resilience, management and planning principles for complex systems, and
applicable elements of reserve theory that may be important in the face of
climate change. The scope of this paper is limited primarily to the scientific
and technical aspects of MPAs and climate change, but it is imperative to
recognise that the political, economic, and social dimensions of MPA planning
and management are equally or more important to their efficacy over the long
The marine environment
properties of the marine environment are different from those of terrestrial
environments in fundamental ways that have implications for the effects of
climate change on oceans and our management actions in response to it. The heat
capacity of water moderates temperature changes in oceans, making changes
slower and of less magnitude than on land, meaning that species inhabit
environments that are relatively thermally stable, particularly in tropical
waters. Water is 60 times more viscous and 850 times denser than air, which
provides buoyancy, permitting a large proportion of marine biota to live most
of their lives in the water column, away from the interface with the geological
substrate (Norse 1993 as cited in Soto 2001). The world’s oceans are also much
larger than the global landbase and life is distributed throughout the entire
water column, meaning that oceans account for 99% of the biosphere, though most
marine life is concentrated close to the sea-air interface (Norse and Crowder
Sea Anemone (Anthopleura elegantisimma). Photo by Brian Klinkenberg.
circulates as air masses circulate on land, although due to its viscosity and
density, it does so more slowly. However, unlike land, many marine organisms
and nutrients exist in the medium which circulates, and there are fewer
barriers to movement through the marine environment (Soto 2001). Thus, species
can be wide ranging and the pelagic larval stages typical of most marine fishes
and invertebrates can be passively dispersed over long distances. This suggests
that marine metapopulation dynamics operate over much longer distances than
terrestrial ecosystems, ecologically linking larger areas (Lipcius et al.
The types and sources
of primary production are also very different between land and sea. Marine
primary production is dominated by microscopic phytoplankton that reproduce
rapidly at a high turnover rate, limiting the standing stock to an average of
1% of annual production (Ricker 1968). There is no accumulation of biomass over
years or decades as there is in plants and trees on land - primary producer
biomass is processed quickly by consumers or reducers (Day and Roff 2000). The
rapidity of primary production combined with the fluidity of water that can
concentrate nutrients and transport species make biological responses to
environmental changes tightly coupled. Short generation times link population
and community cycles more closely to physical processes. This creates an
interesting juxtaposition of quickly responding marine biotic communities
within a slowly changing, insulating ocean - a contrast to longer lived, slower
responding terrestrial communities that exist in a physical environment
characterised by comparatively rapid changes of greater magnitude (Day and Roff
2000). Accordingly, marine communities are expected to respond more rapidly to
climate change than terrestrial environments (Soto 2001).
In addition to the
natural features of marine environments, there are also important features of
our relationship to them. Humans are awkward visitors to marine environments.
Ocean research is expensive, difficult, potentially dangerous, and incapable of
meaningfully investigating all aspects of oceans, given their vast breadth and
depth. Nothing happening below the surface is directly observable which means
that a concerted effort is required to collect information (Norse and Crowder
2005). It also means that the dynamics and health of this alien environment are
easily put ‘out of sight and out of mind’, particularly given that the majority
of humans have little direct interaction with oceans (Day and Roff 2000).
Partly as a result of these factors, less research is conducted on marine
environments than terrestrial ones, further limiting our understanding of their
dynamics (Norse and Crowder 2005).
China Rockfish (Sebastes nebulosus). Photo by Brian Klinkenberg.
Effects of climate change on oceans
Physical and chemical processes
Ocean conditions vary
naturally across a range of temporal and spatial scales. Seasonal changes in
sea surface temperature may be local or regional, the El Niño Southern
Oscillation varies interannually, and the North Atlantic and Pacific Decadal
Oscillations cycle over decades, affecting large ocean areas. The distribution
of species and communities reflects this variation, and changes in biotic
communities in response to natural shifts in ocean conditions are well
documented. Human-caused climate change, stemming primarily from increased
levels of CO2 and resultant increases in atmospheric temperatures,
introduces a new driver of variation in ocean conditions that will alter ocean
temperatures and ocean chemistry with cascading effects on ocean processes and
biotic communities. There are several different methods of exploring potential
impacts of climate change on marine environments (Soto 2001). First, historical
analogies can be developed using sources of information such as
palaeoecological data. Second, research can draw from recent datasets, which
provide less than 100 years of data for most variables. Though a brief period
climatically, it is long enough to demonstrate changes in temperature and
responses in biotic communities. Third, modeling can develop predictions based
on current trajectories and understanding of natural systems processes and
causal mechanisms. They typically include a range of proxies that draw from
either of the data types outlined above or theoretical deduction. Proxies are
selected based on availability and the model’s objective(s), level of
complexity, and resolution (Rahmstorf 2002). Though limited in their ability to
inform our understanding of changes for which we have no analogous experience,
all of these methods are present in the summary of effects outlined here.
Ocean warming and sea
level rise, the two most commonly cited effects of climate change on oceans,
will be accompanied by a host of other physical changes. Atmospheric
circulation patterns will affect patterns of precipitation which may alter
ocean salinity, turbidity, and inputs of terrestrially-derived nutrients washed
into the ocean by precipitation-driven runoff (Harley et al. 2006). Bakun
(1990) forecasts increased winds as a result of comparatively greater heating
over land than water as atmospheric temperatures rise. In wind-driven coastal
upwelling systems such as the California coast, this could increase upwelling.
Snyder et al.’s (2003) regional climate model predicted that upwelling in this
system would increase with rising CO2 concentrations and an
increased temperature gradient between land and sea. This contributed to the
alongshore winds which drive upwelling. However, these dynamics may be somewhat
offset by rising sea surface temperatures and increased freshwater inflows
(from glacial melt) resulting from warmer atmospheric temperatures, both of
which increase the stability of the water column by increasing the buoyancy of
surface water (Roessig et al. 2004). A more stable water column can repress
upwelling (Roemmich and McGowan 1995).
Climate change will
likely affect patterns of ocean circulation. Currents are driven by winds,
thermohaline circulation (THC), or tidal influences (Roessig et al. 2004). THC,
the slow, large-scale movement of deep ocean water masses, is the result of
water density gradients (Hansen et al. 2004). Thus, changes in temperature and
salinity mentioned above may have implications for the persistence of THC
patterns, particularly in the north Atlantic. Relatively faster warming at the
poles is melting ice in northern latitudes, which increases freshwater inputs,
decreases salinity, and increases surface water buoyancy. This may stem the
sinking of typically denser, colder ocean water in the north Atlantic that then
travels south to displace deep water which in turn rises and travels north
(Hansen et al. 2004). The warmer southern water which travels north transports
enormous quantities of heat that keep much of western and northern Europe warmer than they would be otherwise (Rahmstorf 2002). The possibility of weakening
THC in the north Atlantic remains unclear, though its relationship to other
large circulation patterns make the implications of its future function global
in scope (Vellinga and Wood 2002). In the Pacific, a global climate model
forced by a future scenario of increasing greenhouse gas concentrations
forecasts more frequent occurrences of El Niño conditions and a strengthening
of the equatorial thermocline (Timmerman et al. 1999). El Niño brings warmer
water that is lower in nutrients to the west coast of the Americas, and has feedback effects on global climate systems.
Frilled anemone (Metridium senile). Photo by Brian Klinkenberg.
Harley et al. (2006)
suggest that climate-induced changes to the chemical composition of oceans may
have greater impacts on the performance and survival of many species than
temperature changes. Rising levels of atmospheric CO2 have lead to
higher ocean uptake of CO2 and acidification of ocean water (Feely
et al. 2004). Projected atmospheric concentrations of CO2 acidification
are expected to rise from current levels of approximately 380 ppm (Sabine et
al. 2004) to between 540-970 ppm, which may cause a drop in surface water pH of
.4 by the end of the century - a magnitude of change in the oceanic CO2 system
probably unique within the past 20 million years (Feely et al. 2004). The
upward trend in CO2 concentrations will continue to decrease the
degree of saturation of the alkaline minerals aragonite and calcite in the
oceans- minerals that are essential for the multitude of marine organisms that
form calcium carbonate (CaCO3)-based skeletal structures. This
decrease will be greater at higher latitudes (Feely et al. 2004).
responses and implications
Summaries of the
ecological responses to changes in the abiotic ocean environment are arranged
by climatic variable, with consideration of proximate effects primarily at the
individual and population levels (Harley et al. 2006). The summary is not exhaustive
- it focuses on key variables with the most relevance and importance for MPAs.
It is worth noting that some of the most powerful effects may arise from the
interactions and feedback between different stressors. The exponentially
increasing complexity of these interactions makes accurate predictions
practically impossible, though even exploring potential directions and
magnitudes of change can be useful. Broader level outcomes resulting from
multiple factors are considered last in the section on emergent effects.
The effects of
climate change-induced temperature increases on different species will likely
be highly variable and conditional. Species responses in terms of performance
and survival may also not be linear. Temperatures at the extreme ends of
species tolerance ranges can decrease foraging, growth, and fecundity, and
affect migratory behaviour, which in turn can influence population and
community dynamics via their implications for performance, resource use patterns,
and survival (Roessig et al. 2004). Perhaps the most well-known example of the
effects of increased seawater temperatures is the widespread coral bleaching
that has occurred throughout the tropics during anomalously warm periods
(Hughes et al. 2003). Rising seawater temperatures also coincided with
decreased reproductive output and a mismatch between the larval production of
bivalves and peak food supply that increased competition (Philippart et al.
2003). These outcomes resulted in reduced recruitment and smaller adult
populations (Philippart et al. 2003). Species distributions have also changed
with rising temperatures, moving towards the poles to remain within their
optimum temperature range (Parmesan and Yohe 2003). Perry et al. (2005) used
historic fisheries and ocean temperature data to demonstrate that centres of
abundance for two thirds of the North Sea demersal fishes included in the study
have shifted northward over the past 25 years as ocean temperatures increased
approximately 1°C in the same period. Those species whose distributions shifted
had faster regeneration times, which may suggest that other species have simply
been slower to respond. However, Schiel et al. (2004) warn that the theory that
warm water species will replace colder water species as temperatures rise does
not always hold true. In their study of elevated sea temperatures caused by
thermal discharge of a power plant, communities were altered as key
habitat-providing kelp species declined with higher temperatures, and other species
abundances increased. The community changes did not correspond with a shift
toward warmer water species, and was not adequately explained by ecological
interactions, highlighting our limited understanding of complex ecosystems’
responses to change (Schiel et al. 2004).
Green Turtle (Chelonia mydas), photo by Brian Klinkenberg.
Sea level rise
The predicted effects
of rising sea levels include a reduction in some areas of intertidal habitat
due to steep coastline topography and the proliferation of anthropogenic
structures such as seawalls and groynes (Galbraith et al. 2002). Projected
rates of sea level rise may also outstrip the rate at which biogenic habitats
such as marshes, seagrass beds, and coral reefs are capable of shifting or
accreting (Knowlton 2001). Due to the dependency of these systems on sunlight,
they may drown as sea levels rise above them and the overlying waters attenuate
more sunlight. The death and decay of these habitat-forming species complexes
would have dramatic effects on the diverse species that live primarily or
exclusively in association with them; coral reef-associated species may number
between 1-9 million (Knowlton 2001).
Changes in ocean
Increased mean wind
speeds and increased frequency of extreme wind events will have strong impacts
on shallow subtidal and intertidal communities (Harley et al. 2006). This may
exacerbate the pressures on biogenic habitats such as marshes, seagrass beds,
and coral reefs mentioned above, as well as kelp forest ecosystems, all of
which can be damaged by wind-driven storm waves. These multispecies complexes
perform a range of functions related to biodiversity and production - they
provide habitat and refuge, act as nurseries for young fish, and retain larvae
and detritus (Boesch and Turner 1984; Carr 1989; Pakhomov 2001). Increased
intensity and frequency of wind and waves could reduce the recovery of damaged
coastal ecosystems between disturbance events and also result in a shift in
dominant species towards those that are faster growing or more resistant to
damage (Harley et al. 2006).
Marine ecosystems are often dominated by
organisms with planktonic life history stages, which make the composition of
those ecosystems sensitive to oceanographic patterns that disperse and
concentrate larvae (Harley et al. 2006; Day and Roff 2000). Those same patterns
also play a role in concentrating, enriching, and retaining nutrients in
different areas, which has implications for the production, species
composition, and species diversity at a given site as well as the distribution
and abundance of species among sites (Bakun 1996). Gaylord and Gaines (2000)
observe that clusters of range boundaries of coastal marine species occur where
ocean currents meet and suggest that the flow patterns of the currents
themselves (in addition to the current’s water properties) may play a role in
determining species distribution patterns. Thus, currents can constrain species
distributions even when suitable habitats exist elsewhere (Gaylord and Gaines
2000). If circulation changes shift current patterns, species distributions
could also shift- due to distribution into previously ‘out of reach’ but
suitable habitats, or because of the species associated with the water
conditions particular to a given current. Conversely, if water temperatures
rise beyond a species’ tolerances, but they are not dispersed to more suitable
habitats by currents or advection patterns, local extinctions may occur.
Changing current and circulation patterns may also serve to facilitate the
spread of invasive species (Harley et al. 2006).
CO2 concentrations and pH change
systems, increasing CO2 concentrations will not increase production
through increased photosynthesis because most marine primary producers are
carbon saturated (Harley et al. 2006). However the acidification of the oceans
due to increased CO2 uptake and associated decrease in the
availability of CaCO3-forming minerals will limit the rate of
biogenic calcification- the rate at which calcifying organisms form their
skeletal structures (Feely et al. 2004). These include primary producers,
coccolithophorid zooplankters, corals, coralline algaes, crustaceans, and
molluscs (Harley et al. 2006). The population and community-level impacts of
potential CO2 changes are largely unknown (Harley et al. 2006).
However, the possibility that coral reefs at the northern and southern edges of
the global coral range could lead to a shift (rather than a shrink) in coral’s
distribution- as sea temperatures outside their current range warm and become
favourable- may be hampered by the comparatively larger impacts of increased CO2 concentrations on waters at higher latitudes (Kleypas et al. 1999). These
increased CO2 concentrations mean less availability of the CaCO3-forming
minerals essential for the growth of reef-building corals.
Mottled Star (Evasterias troschelii ), photo by Brian Klinkenberg.
Harley et al. (2006)
identify four fundamental groups of emergent effects of climate change on
marine biota and biological processes, all of which are interconnected: shifts
in species distributions; changes in species composition, diversity, and
community structure; changes in primary and secondary production; and changes
in population dynamics and evolution.
Shifts in species
distributions may be vertical or biogeographical. Species distributions in
intertidal and nearshore benthic habitats are strongly vertically stratified,
and changes in temperature or light conditions with rising water levels may
cause some species to shift into the vertical zones of other species (Harley et
al. 2006). These shifts may cause competitive exclusion of certain species if
they are, for example, caught between competitive stress from below and
temperature or exposure-induced stress from above (Mathieson et al. 1998;
Harley et al. 2006). Biogeographical shifts can occur in a number of ways. Some
species exhibit behavioural thermoregulation, actively seeking temperatures
that are within their optimal range, though these preferences may be tempered
by other environmental factors such as food availability (Roessig et al. 2004).
Community level interactions between species may change at range boundaries,
also shifting species distributions as a result of synergistic effects of
multiple stress factors. For example, warmer waters are generally more
conducive to the spread of pathogens (Harvell et al. 2002). For species at the
warmer boundary of their range, the compounding stresses of rising water
temperatures and the incursion of pathogens may suffice to decimate the local
population. These changes also highlight a way in which community composition
may change. Schiel et al. (2004) documented significant changes in the
diversity and composition of nearshore communities in response to higher
temperatures. Species respond to environmental changes individually at their
own speed and direction, and thus, biological communities do not necessarily
move as units. Communities may disassemble, with new ones reforming (Lovejoy
circulation patterns play a key role in shaping primary production. Changes in
these patterns will alter the locations of fronts, where production is high,
and the intensity of upwelling at shelf and coastal locations, which bring
cold, nutrient-rich water to the surface and drive productivity. An increased
frequency of El Nino events, which discourage upwelling, would have significant
negative impacts on anchovy production on the South American coast. The
anchovy, which is the target of one of the largest-volume fisheries in the
world, is associated with the colder, nutrient rich upwelling regimes off the
South American coast (Alheit and Niquen 2004). Climate change may also cause
shifts in the timing of seasonal stratification of seawater, with warming
potentially causing stratification earlier in the spring and mixing later in
the fall. This in turn may mean that different organisms whose life cycles
correspond (or adapt more quickly) with the altered timing of highest
productivity become more dominant (Soto 2001). Organisms with faster generation
times are expected to have quicker responses to climatic changes (Berteaux et
al. 2004). Changing currents and circulation patterns will also have
implications for the dispersal of genes among populations, with potential
impacts on the genetic diversity of species and their abilities to adapt to
changes in their environments (Harley et al. 2006).
Spotted Ratfish (Hydrolagus colliei), photo by Brian Klinkenberg.
role for marine protected areas
The rationality of MPAs as a long-term
conservation measure in the face of climate change will depend on the purpose
that governing agencies and societies define for them. When their purpose is
clearly outlined, their efficacy in achieving that purpose amid changing
environmental conditions can be meaningfully examined. MPAs have a range of
potential functions that include conserving biodiversity, facilitating tourism,
protecting habitats, providing refuge for fished species, enhancing production
of target species, providing a management framework for sustainable multiple
use, acting as sites of scientific research, and demonstrating the extent of
human impacts on marine ecosystems (Allison et al. 1998). The term MPA also
covers an array of spatially explicit management measures that vary in their
degree of protection. Thus, the concept of an MPA is somewhat malleable, and
their goals and purposes have often been unclear (Agardy et al. 2003; Willis
2003). Further, priorities have often remained unstated for the many MPAs that
have multiple objectives. Limited resources usually preclude detailed attention
to all of them, some objectives may compete (e.g., biodiversity conservation
and target species enhancement), or climate change may force choices about what
Some of the MPA
functions outlined are less directly focused on biological objectives and serve
a more managerial or educational role. Climate change may have less direct
implications for the efficacy of MPAs that make these functions their primary
objectives. However, the majority of MPAs state biodiversity conservation
and/or sustainable fisheries management objectives among their priorities (Ray
2004). For these reasons, I focus on MPAs whose primary objectives are
biological in nature, and I accept that the conservation of resources and
biodiversity is a broadly agreed-upon, desirable objective.
The preceding summary
of potential effects of climate change on oceans makes it clear that any given portion
of the world’s oceans is likely to experience numerous types of change in the
future. As protective measures particular to portions of the ocean, the content
of what MPAs “protect” is therefore also likely to change, potentially in ways
that are deemed undesirable- hence the rationale for this examination of their
capacity as conservation tools. Despite these possibilities and the inability
of MPAs to protect against these boundary-less threats, they remain a useful
and important long-term conservation tool because (1) they provide unique
protection for marine ecosystems that may serve to increase the resilience of
those ecosystems to perturbations caused by climate change, (2) they can
function as control sites that can help discern causal agents of future change
(Soto 2001), and (3) the creation of marine protected areas can raise the
profile of marine ecosystems (Cocklin et al. 1998).
MPAs are just one of
many marine conservation strategies that address the variety of human stressors
on oceans. Other strategies include pollution prevention initiatives, coastal
development restrictions, harvest bans on certain species, and restrictions on
fishing gear, effort, and season, all of which have been used around the world,
in some cases for decades or centuries. MPAs are effective in controlling
different kinds of local impacts, though the focus has been on their potential
to serve as refugia from fishing pressure, and several authors have indicated
that this is where their greatest conservation value lies (Roberts and Polunin
1993; Allison et al. 1998; Agardy 2000). Their potential in this regard is
important in light of the strong evidence that fishing constitutes the greatest
current threat to marine ecosystems (Pauly et al. 1998; Jackson et al. 2001; Myers
and Worm 2003; Pandolfi et al. 2003; Crowder and Norse 2005). If mitigating
fishing pressure is where MPAs are most effective, and fishing is the most
important current human impact on the world’s oceans, it is appropriate to
focus on the long-term capacity of MPAs with respect to these factors.
Critically assessing whether or not MPAs are a useful long-term conservation
tool should also entail weighing their capabilities against other conservation
options, again with a focus on these factors.
Moon Jellyfish (Aurelia labiata), photo by Brian Klinkenberg.
MPAs are unique in
that they can offer permanent spatial protection that prohibits some or all
human activities. This preserves the abundance, species richness, species age
structures, and habitats of communities to an extent that other measures do
not. Put differently, the natural variability, or biodiversity, of the
community at the site is more comprehensively protected. Though measures such
as fishing effort limitations or gear restrictions may reduce and minimise
effects on communities, fishing still selects for species and size, generally
first taking bigger, older individuals thereby altering age structures and
reducing the system biodiversity (Hilborn and Walters 1995). Decreasing
diversity within a system can lead to less resilience. Resilience is a term defined
in several ways, but thought of here as a measure of a system’s creative
ability to sustain itself- to absorb perturbations and maintain function
(Holling 1986). Although a full discussion of the concept and empirical support
for resilience is beyond the scope of this paper, key functions of resilience
and its relationship to biodiversity as they pertain to MPAs and climate change
are included here. The relationship between biodiversity and resilience stems
from the ecological functions that species perform. Each species is capable of
performing a limited number of ecological functions, and as species are added
to an ecosystem, more ecological functions accumulate, generating functional
diversity (Peterson et al. 1998). With continued species additions, species
functions may begin to overlap, creating functional redundancy which can
increase ecological stability; the ecosystem develops the capacity to sustain
disturbances to some species without a total loss or impairment of ecosystem
functioning (Peterson et al. 1998). Although there are different theoretical
models for the relationships between biodiversity and ecological stability
(e.g., rivet, idiosyncratic, keystone), these underlying principles are
similar. Diverse systems may also be faster to re-establish ecological
functions when they are impaired or lost.
testing of the relationship between biodiversity and resilience in situ is challenging, perhaps most so for large, pelagic systems with few spatially
stationary elements. Testing would require similar ecosystems with varying
levels of biodiversity, the measured application of disturbances, and the
monitoring of system responses, all the while controlling for the myriad other
factors affecting ecosystems, and preferably at the large scales that interests
society (Raffaelli 2006). However, there is other evidence that suggests
altering the natural variability of marine ecosystems impairs the structure and
function of those systems, that the losses of functions can have negative
impacts on ecosystem goods and services of interest to humans, and that more
diverse systems with all functional groups present recover faster from
disturbance, including thermal disturbance (Bythell et al. 2000; McClanahan
2000; Allison et al. 2004; Dulvy et al. 2004; Worm et al. 2006). A well-known
marine example derives from Caribbean coral reefs, where overfishing of
herbivorous fishes lead to a population explosion in another herbivore, the
black-spined sea urchin. Herbivory, which keeps algal growth on corals in
check, continued. However, diversity and functional redundancy in the ecosystem
had been reduced. When a pathogen killed over 90% of the sea urchins throughout
the Caribbean, the ecological function of herbivory was drastically impaired,
enabling a shift in the ecosystem away from a coral reef-dominated state to an
ecosystem dominated by macroalgaes which supports less fish (Grimsditch and
Salm 2006). Thus, the loss of diversity reduced the resiliency of the coral
reef ecosystem and left it less able to sustain function in the face of
subsequent disturbance, which resulted in a shift away from that ecosystem
What role do MPAs
play with respect to climate change, biodiversity, and resilience? While
functional redundancy within marine ecosystems appears to vary naturally, fully
protected MPAs have been found to host higher species diversity and higher
levels of functional diversity than surrounding areas (Clark and Warwick 1998;
Micheli and Halpern 2005). Though MPAs do not prevent the spread of warmer
waters resulting from climate change, they can play a role in reducing the
number of other stressors present in a marine environment. MPAs can thus
facilitate the maintenance of higher degrees of ecosystem resilience in those
locations, putting those ecosystems in a better position to absorb climatic
perturbations. A role for them in this respect is clear in the following
climate-related example outlined by Hughes et al. (2003): anthropogenic impacts
on coral reefs including overfishing of herbivorous fishes, excess nutrient
inputs, persistent physical disturbance that increases coral mortality, and
increased levels of disease all impair the ability of corals to recover from
acute disturbance events such as coral bleaching that result from high water
temperatures. Water temperatures at the extremes of coral tolerances are
expected to become more common as atmospheric and sea temperatures rise with
global warming. Reducing the magnitude of other human impacts promotes higher
levels of reef resilience to climate change-related disturbances.
There are several
signs that the relationship between climate change and fishing is key for
marine ecosystem health. Fishing and climate change may act synergistically to
reduce fish populations to such a small population size that they cannot
recover (Scavia et al. 2002). Climate or fishing accounted for the primary
forcing mechanism in 27 of the 29 Large Marine Ecosystems assessed for forces
driving change in biomass yields (Sherman 2006). Based on a review of the
effects of climate and additional stressors on marine environments, Harley et
al. (2006) suggest that marine ecological responses to climate change will
depend primarily on fishing pressure. These indicators underscore the role for
MPAs given their capacities to act as fishing refugia.
Soto (2001) suggests
that MPAs may also have an important role to play as control sites that can
help to separate out causal factors like coastal development or fishing from
the effects of climate change on marine ecosystems, thus facilitating
scientific understanding of the effects of climate change on marine
environments. This purpose may blend well with the functions that MPAs can
serve as sites of scientific research. Additionally, the creation of MPAs has
heightened interest in marine ecosystems, leading to increased tourist visits
in areas and sentiments among adjacent communities that local MPAs have raised
environmental awareness (Dixon et al. 1993; Cocklin et al. 1998). Insofar as
this interest and awareness facilitates an understanding of the links between
marine ecosystem health and global climate change, the existence and
proliferation of MPAs may have the potential to contribute to a societal
willingness for behavioural changes that reduce greenhouse gas emissions.
Red king crab (Paralithodes camtschatica), photo by Brian Klinkenberg.
Effective marine protected areas
for the future
The preceding section
demonstrates that MPAs can be useful long term conservation measures. However,
the evidence provided does not mitigate the challenges that climate
change poses to the efficacy of MPAs; it primarily demonstrates how they can be
useful in spite of climate change. This section will explore how MPA
planning and management can be approached in order to better prepare and cope
with climate changes- that is, how climate change challenges for MPAs can be
mitigated. I outline three related tenets that can function as central guiding
themes for MPA planning and management. The first two, uncertainty and the
precautionary approach, detail an appropriate ‘mindset’ for approaching MPA
choices, and the third, adaptive management, provides a model for the
management of MPAs through time as conditions change. The section closes with a
series of specific recommendations about how MPA planning and management can be
changed for increased long-term efficacy in achieving biodiversity
conservation. Recommendations are aimed primarily at national and state
government agencies responsible for conservation or resource management, though
other MPA practitioners will also find them applicable. These levels of
government are most commonly those with the jurisdiction, the mandate, and the
capacity to implement MPAs.
The complexity of the
atmospheric, oceanographic, and ecological systems relevant to MPAs prevents
our ability to understand them perfectly and predict their future states with
certainty. There is also uncertainty in our understanding of what human
activities are conducted in marine environments systems and how they affect
marine systems (Lauck et al. 2004). Uncertainty is particularly prevalent in
managing and conserving marine systems because of several characteristics
mentioned earlier: marine communities are not directly observable; data
collection is difficult, expensive, and therefore sparse; and most species’
life histories involve a larval stage that is prone to variable dispersal over
potentially large distances (Botsford and Parma 2005). Chaos theory suggests
that this unpredictability is an inherent property of complex systems, and that
pursuing more detailed understanding of these systems cannot resolve this
(Hilborn et al. 1995). The enormous number of interacting components in these
systems and the feedback mechanisms between them mean that even slight errors
or imprecisions in our calculations of their initial conditions can quickly compound
and lead to very different futures than those anticipated (Cartwright 1991).
The uncertainty that pervades all of our knowledge regarding these natural
systems, and the decisions we make with respect to them poses a major challenge
to MPA planning and management. It makes clear that we cannot assume that, with
enough information, we can anticipate what will happen and determine how to act
to promote or discourage projected changes, such as those stemming from climate
change (Cartwright 1991). Instead, uncertainty must be explicitly acknowledged
and taken into account during scientific analyses and management decisions (FAO
1995). Predictions can be developed as a range of probabilistic outcomes based
on repeated iterations of models. Cartwright (1991) recommends that even the
model’s initial conditions should be varied, as we cannot assume that we have
perfect knowledge of the present state. Planning can then explore plans for
dealing with different futures, and dealing with the unexpected.
There are three
standard responses to the risks posed by uncertainties (Peterman 2004). First,
we may make optimistic assumptions about the impacts of human activities on
marine ecosystems and act aggressively, harvesting or polluting with little
concern for conservation. Second, we may suggest that our incapability of fully
understanding our impacts on the ecosystem means that we should do nothing-
frequently used as an argument for maintaining the status quo. Third, we can
make a more pessimistic assumption about human impacts on the ecosystem and act
cautiously, building in buffers that allow for our assessment of the system
state and prediction of its response to disturbance to be wrong to some degree.
Given the importance of marine ecosystem goods and services, and our poor
record of marine conservation to date, a precautionary approach is a sensible
response to the risk that uncertainty poses. The implementation of MPAs can be
understood as a precautionary measure, or hedge, against the risks of
uncertainty (Lauck et al. 2004). But further, a precautionary approach suggests
that the design of the MPAs themselves also incorporate precaution, such that a
buffer is built in to better ensure that they achieve conservation objectives.
The last tenet that
should guide MPA planning is adaptive management, a management model which
acknowledges uncertainty and ‘learns by doing’ (Ludwig et al. 1993). There is
an explicit role for monitoring and making adjustments based on results of
previous decisions, and future modifications to the management approach are
anticipated (Botsford and Parma 2005). This is in contrast to other management
approaches which do not systematically question the knowledge of the marine
system upon which decisions are based, nor consciously approach decisions as
iterative experiments (Parma 1998). Adaptive management is well suited for
situations where learning by observing past instances of similar problems is
not possible because problems are new, as is the case with climate change
(Hilborn et al. 1995). The uncertainty of (1) how global climate will change,
(2) how this will affect marine systems, and (3) what this means for MPAs,
combined with the certainty that change will occur, demands that
planning and management of MPAs ‘plan for surprise’ and adapt if they are to
remain effective amid changing environmental conditions (Holling 1986). Though
adaptive management has drawbacks such as the difficulty of detecting ecosystem
change and the political risks of constant management alterations, it is the management
model best suited for planning for surprise and adjusting to the ecological
changes caused by climate change (Suffling and Scott 2002).
Parks Canada’s review
(Suffling and Scott 2002) of the implications of climate change for national
parks is reflective of the rationale outlined here. In a review of policy
directions for protected areas in the face of climate change, Parks Canada
identified four options:
1) static management:
manage and protect current ecological communities within current parks, using
2) passive management:
accept ecological responses to climate change and allow processes to take place
3) adaptive management:
maximise the capacity of species and ecological communities to adapt to climate
change through active management interventions.
some combination of the above options.
Options one and two
were ruled out as (1) unfeasible given the probability of change and (2)
unpalatable given the likely opposition to the loss of symbolic species or
places, respectively. The authors recommended pursuing adaptive management as
the best means of achieving the goal of preserving ecological integrity. Kay
and Schneider (1992) define ecological integrity as “the ability of an
ecosystem to self-organise over a broad range of organisational levels and
spatial-temporal scales”. This concept of ecological integrity is closely
related to that of resilience- a key reason for the use of MPAs and a property
of marine ecosystems that MPAs should attempt to maintain. This paper supports
Suffling and Scott’s (2002) suggestion that adaptive management is the most
appropriate approach for managing MPAs to ensure that the resilience of
protected ecosystems is maintained.
light of the likely effects of climatic change on marine ecosystems, nine
recommendations are outlined here that operationalise the guiding themes for
planning and management detailed above:
1) Create more, sufficiently large MPAs to hedge
against stochastic events, management errors, and human impacts (Soto 2001).
Fewer, larger MPAs are generally preferable to many smaller MPAs, and in the
absence of specific factors suggesting the contrary, this is an appropriate
guideline to follow (Frid et al. 2006). Criteria for determining sufficient
size have yet to be defined in MPA design theory, but will vary according to
the targets of protection and ecosystem attributes. One model developed for the
Gulf of California calculated that reserves needed to be at least 50 km2 in order to retain significant proportions of fish and algal larvae (Sala et
2) Build insurance factors into the design of
MPAs so that there is more of each desirable ecosystem feature than deemed
necessary under current conditions- this is especially applicable for
quantifiable features (e.g., the total area of x habitat desired within
the park) (Allison et al. 2003). Replicate the protection of conservation
targets where feasible to diversify and mitigate risk (Salm et al. 2005).
Consider sites that may be less affected by certain effects of climate change
such as increased storm frequency.
3) Integrate planning and management of MPAs
within a broader coastal zone management framework (Cicin-Sain and Belfiore
2005). This may help in planning for and limiting the boundary-less stressors
that affect MPAs from surrounding waters.
4) Consider how MPAs may be networked for
functional linkages when planning, and coordinate MPA planning between
different agencies to facilitate this. Functionally linked networks across
latitudes could allow for species distributions to shift and remain partially
protected. Connectivity in this respect is more difficult to define for MPAs
than terrestrial protected areas. Dispersal patterns of larvae are an important
link between MPAs that can replenish disparate populations, and are essential
to consider in network design (Botsford and Parma 2005). Thus, hydrography,
distance between sites, and ‘downtream’ or ‘upstream’ dispersal dynamics with
respect to other reserves and management areas may be critical (Frid et al.
2006). Conversely, while MPAs should be close enough to be functionally linked,
planners should also consider adequate spacing to reduce the risk that one
catastrophe might impact multiple MPAs (Roberts et al. 2003). This may be
particularly relevant given predictions of increased frequencies of extreme
5) Plan for representativeness of ‘enduring
features’ that play roles in shaping community types in MPA networks. This may
be a more effective strategy for maintaining representativeness of future
biological communities than planning based solely on the current distribution
of biotic communities, which is likely to change (Day and Roff 2000).
6) Recognise that the implementation of MPA
networks is a long-term, sequential process. This acknowledges the uncertainty
surrounding future MPA opportunities with respect to (1) where and when
conservation opportunities will arise, (2) budgets for conservation
initiatives, and (3) the degradation, loss, or shift of conservation values
(e.g., biodiversity) at different sites due to effects of different stressors,
including climate change, over intervening periods (Meir et al. 2004). This is
a more adaptive approach that fosters a move away from a static blueprint for
an optimal MPA network based on a snapshot in time, and enables the design of
each component of a MPA network to reflect any situational changes and enhanced
understandings that have evolved since previous choices.
7) Identify communities that have demonstrated
resilience to past warming events. This is particularly relevant for coral reef
MPAs, where reef responses to recent extreme temperature events have
demonstrated variable resistance to and recovery from coral bleaching (Salm et
8) Consider flexible MPA boundaries, especially
for MPAs zoned for multi-use, where highly protected core areas could be
expanded without requiring more potentially politically difficult changes to
the total area of the MPA (Peters and Darling 1985).
9) Make planning incremental as chaotic systems
can be better understood at the local, incremental level (Cartwright 1991).
This approach is closely linked to the iterative focus of recommendation 6.
exist for understanding the effects of climate change on oceans and planning
for, or evaluating the value of, MPAs accordingly. Humans are attempting to
understand how systems change in response to environmental conditions for which
there is no real analogue (Harley et al. 2006). There is also the potential for
non-linear, non-independent, unpredictable, and dramatic changes- properties
characteristic of complex systems such as atmospheric, oceanographic, and
ecological systems (Southwick 1976; Schneider and Kay 1992). Climate-related
examples of these changes already exist for marine biota’s responses to
environmental change (Reynaud et al. 2003; Hsieh et al. 2005). Even where the
causes of certain changes can be determined, removing or mitigating the cause
will not necessarily return the system to its former state, as changes are not
always reversible (Knowlton 2001). Changes may also favour some life history
strategies over others, such as generalist or opportunist species that are
readily able to adjust their diets and habitats, which may make these species
less in need of conservation attention than others (Harley et al. 2006).
MPAs are one
component of a marine conservation strategy that will need to include many
other measures in order to adequately conserve marine ecosystems. Managers and
planners will need to think strategically about MPA conservation priorities and
adaptively direct effort where it is feasible and can make the largest or most
essential differences to the conservation values that society has deemed most
important. They will also have to think carefully about what the different uses
of MPAs mean when taken together; if MPAs are valued as control sites to
determine causes of ecological change, what does this mean for an adaptive
management approach that will adjust management to promote resilience and
ecological integrity? Can MPAs still be thought of as benchmarks in this case?
Given the intensive information and management requirements of adaptive
management, are fewer MPAs that are better monitored a preferable strategy to
many MPAs with less monitoring? Thompson et al. (2002) also point out that
other stressors should not be overlooked, as those with the most potential to
further degrade some marine environments in the foreseeable future are already
familiar to us: pollution, coastal development, fishing practices, introduced
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