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Tag Archives: Ecosystem Services
Without a Seaweed Meadow
Ascophyllum nodosum is a brown seaweed and a ubiquitous member of intertidal communities throughout the temperate North Atlantic. This cold- and calm-water loving species has long strappy branches and air bladders along its axis. It grows in dense stands that are up to a meter tall – forming beautiful floating meadows at high tide and thick, floppy mats of seaweed at low tide. Ascophyllum’s high abundance, canopy formation, and place at the bottom of the food-chain makes it an important foundation species for intertidal rocky shore communities. So what would happen if Ascophyllum was suddenly gone tomorrow?
An aerial view of an Ascophyllum dominated intertidal community at low tide. Eager phycology students head down to survey the diversity at Quoddy Head State Park, Maine, USA. (C) Kylla Benes
Fortunately, there have been a few classic and long-term studies* that have addressed this question. Clearly, the removal of any foundation species would result in an immediate decline in associated and dependent species. But what about the long-term changes in intertidal communities?
First a little lesson on intertidal community organization. For sessile (attached and non-mobile) organisms, competition for space is a key driver of diversity on rocky substrate. Recruitment rates, growth rates, longevity, and position in the food-chain can determine which species are most abundant. Ascophyllum is not very good at recruiting. But its density, height, long life-span (up to 100 years), and low palatability mean that this species can out-compete many other sessile seaweeds and invertebrates. Large disturbances—such as strong waves or ice scour — that can remove Ascophyllum and/or high recruitment of other sessile species can lead to other seaweed and invertebrate species becoming dominant. Importantly, the identity of the dominant species can have major impacts on the associated community.
At locations where there is little recruitment, such as the northern-most reaches of the Gulf of Maine, the removal and absence of Ascophyllum could result in a mostly barren landscape or a sparse and low diversity community at best. At locations where there is high recruitment of invertebrates, barnacles and mussels can form near monoculture beds that provide little habitat for the intertidal community that is characteristically associated with Ascophyllum. Although, micro-invertebrates that can live in the interstices between mussels and predators of barnacles and mussels would be happy. In particular, mussels can become so dominant and persistent, that they can form stable and alternative intertidal communities to the Ascophyllum-based versions communities. At locations where predatory pressure from whelks and crabs is high enough to keep these invertebrates in-check, other brown seaweeds in the genus Fucus can be dominant space holders. As close relative to Ascophyllum, these species can play a similar role in intertidal communities, but they are not as long-lived and are more susceptible to damage from waves and herbivores. In the long-run, Fucus-dominated locations may be less stable compared to Ascophyllum-dominated intertidal communities.
The rocky intertidal at Mill Pond, Swans Island, Maine USA. From the 1980’s to 1990’s mussels and barnacles dominated this site (left). Beginning in 2000, disturbances from ice scour opened up space, allowing for a shift to a seaweed dominated community (right). Arrows indicate reference points at the site. Photos: (C) Steve Dudgeon and (C) Peter Petraitis – To see other photographs and learn more about the long-term studies of alternative stable states in the Gulf of Maine, visit the LTERB website.
The above, are all direct effects of the loss of Ascophyllum on the structure intertidal communities but there would also be some indirect effects. Many birds, fish, and invertebrates use Ascophyllum meadows as temporary habitat during migration or as juveniles. Further, seasonal release of gametes and senesce of Ascophyllum may be a large source of nutrients and carbon for intertidal animals or may even be exported to other ecosystems such as the deep subtidal. With Ascophyllum gone, these animals and ecosystems may suffer. These indirect, but potentially important, effects of Ascophyllum are much less well known and studied than direct effects.
Example seaweeds (A-C) and invertebrates (D-I) commonly associated with Asocphyllum. A) Palmaria palmata, B) Corallina officinallis, C) Ulva lactuca, D) Littorina littorea, E) Testudinium testudinalia, F) Littorina obtusata, G) Botryllus sp., H) Mytilus edulis, I) Semibalanus balanoides.
Photos: (C) Kylla Benes
Lastly, the disappearance of Ascophyllum would result in a loss of many ecosystem services that we humans are reliant upon. Lobster, cod, and several other fisheries species use seaweed meadows as nursery habitat for their young. The sudden disappearance of Ascophyllum would result in a reduction of these species, and ultimately income from these fisheries. And this would result in less of the surf, in your surf and turf dinners. Ascophyllum itself is harvested for use in fertilizer, nutritional and beauty products, and even as packaging to ship lobsters to distant restaurants (leading to a small temporary population in the San Francisco bay area). Last year, over 15 million pounds of seaweed were harvested from the coast of Maine, USA and the products of the seaweed industry are valued at about $20 million per year. In addition to its importance in fisheries, Ascophyllum is a foundation species of biodiversity hot spots (e.g., Cobscook Bay) and may be an important carbon sink, which could help mitigate the effects of ocean acidification.
Whether you’re an ecologist interested in community dynamics, think protecting the Earth’s biodiversity is important, or simply love a lobster dinner, we all have a reason to care about Ascophyllum.
*References on Intertidal Community Organization in the Gulf of Maine
Menge, B. A. 1976. Organization of the New England Rocky Intertidal Community: Role of Predation, Competition, and Environmental Heterogeneity. Ecological Monographs 46:355-393.
Petraitis, P. S. & S. R. Dudgeon. 1999. Experimental evidence for the origin of alternative communities on rocky intertidal shores. Oikos:239-245.
Bryson, E. S., G. C. Trussell, & P. J. Ewanchuk. 2014. Broad-scale geographic variation in the organization of rocky intertidal communities in the Gulf of Maine. Ecological Monographs 84:579-597.
May 31, 2016
Even deleting the chestnut blight won’t necessarily bring the chestnut tree back*
Degrading Forests and Extinction Debts
When I ask my introductory biology or ecology students what they think the biggest threat to Earth’s biodiversity is, climate change or pollution typically get the most votes. Perhaps the (much warranted) public attention and debate on these issues leads students to focus on these particular problems, but in fact, habitat loss and degradation have the largest impact on biodiversity. Further, many of the other major threats to biodiversity (e.g., climate change, pollution, etc.) can be directly or indirectly linked to habitat loss.
It is easy to connect complete habitat loss to loss of biodiversity – if a forest is cleared of trees, the diversity and abundance of associated flora and fauna will likely be reduced. But what about fragmented habitat? How does the size and shape of patches of forest or grassland influence remnant communities and ecosystems? The theory of island biogeography gives us hypotheses of how fragment size and isolation might influence populations and diversity. However, habitat fragments are embedded in an anthropogenically-influenced landscape and just how much that landscape influences the structure and function of the remaining habitat is an important question for conservation.
Nick Haddad and colleagues recently reported on the state of the world’s fragmented habitats; including a meta-analysis of long-term experiments specifically designed to test how area, isolation, and edge (distance to perimeter) of fragments effect the remaining communities and ecosystems. High-resolution satellite data revealed that 20% of the world’s forests were within 100 meters of a forest edge and 70% were within 1 kilometer, meaning most forests today are in close proximity of human activity.
A series of long-term (20+ years) habitat fragmentation experiments (see below), spanning multiple continents and biomes, have provided a data set of 76 studies testing how this proximity to human activity influences ecosystems. Specifically, this synthesis enabled Haddad et al. to test the effects of reduced habitat area, increased isolation, and increased habitat edge on a variety of community and ecosystem variables. Not surprisingly, all three treatment variables had negative effects on processes such as organismal abundance, species richness, pollination, nutrient retention, etc. and reduced habitat area and increased isolation appear to have the strongest effects.
Most striking however, was the accumulated long-term consequences of habitat fragmentation. By comparing changes in species richness, immigration, and ecosystem functions (e.g., biomass, total organic carbon, etc.) over time, a delayed effect of fragmentation appeared. That is, the proportional (negative) change in community structure and function increased over time. The negative effects of habitat fragmentation are not necessarily seen immediately after deforestation, and those effects may get worse over time – extinction and ecosystem function debts yet to be realized.
Large, expanses of forest still exist in South America, Africa, and boreal regions. Given that biodiversity loss itself can have strong detrimental effects on ecosystems, that climate change will likely exacerbate effects of fragmentation, and our economic incentives for protecting habitat, the analysis by Haddad et al. present a strong argument for maintaining these large stretches of uninterrupted forest.
Long-term experiments included the meta-analysis:
Biological Dynamics of Forest Fragments (Brazil, in Portuguese)
Kansas Fragmentation Experiment (USA)
Wog Wog Fragmentation Experiment (Australia)
SRS Corridor Experiment (USA)
Moss Fragmentation (UK, Canada)
Newly established experiments:
Metatron (France)
S.A.F.E. Project (Borneo)
April 1, 2015
Even Better than Gold: The Value of Protected Areas
The implementation of protected areas (PAs) is considered the backbone strategy of efforts towards the conservation of biodiversity and natural resources. Currently, the global network of PAs covers approximately 18.8% of the planet (15.4% of terrestrial and inland water and 3.4% of marine and coastal areas, see Fig. 1), safeguarding millions of species and providing a series of important ecosystem services such as water regulation, carbon neutralization, food, climate change mitigation and adaptation, as well as cultural and aesthetic services. Although many countries have committed themselves to increment the coverage of PAs in the upcoming years through international agreements, such as the Convention on Biological Diversity (which aims to assure that by 2020, at least 17% of terrestrial and inland water and 10% of coastal and marine areas are covered by PAs), they never been so threatened as now! A current, and overlooked, practice known as protected area downgrading, downsizing, and degazettement (PADDD) has become widespread in many countries, threatening and dismantling PAs everywhere due to economic interests such as mining, new power plant projects, etc. (for more information and a global map see here; Also, a while ago, I wrote a post about PADDD in Brazil here). Thus, estimating the economic relevance of PAs and bringing this information to political and socioeconomic discussions has become an urgent task.
Protected areas of the World. Extracted from: Juffe-Bignoli et. al. (2014).
In a pioneering study, Andrew Balmford and colleagues have attempted to estimate annual numbers associated with PA visitation and their local and global economic impact. They compiled data from more than 500 terrestrial PAs from 51 countries and built regional and global models to estimate, among other things, the number of visitors, direct expenditure by visitors (calculated from expenditures with fees, travel, accommodation, etc.), consumer surplus (defined as the difference between what visitors would be prepared to pay for a visit and what they actually spend) and the effect of some explanatory variables, such as PA size, remoteness and national income, that might affect visitation rates. Based on these explanatory variables they could predict visit rates for roughly 100,000 PAs.
Their results demonstrate that PAs receive approximately 8 billion visits/yr. Visitation rates are predicted to be higher in Europe, where PAs would receive a combined total of 3.8 billion visits/yr, and lower in Africa (69 million visit/yr). Associations with individual explanatory variables varied regionally in their effect, but as one might expect, national income is a common factor affecting visitation rates in every region. PAs generate approximately US $600 billion/yr in direct expenditure and US $250 billion/yr in consumer surplus. An older estimative shows that less than U$10 billion/yr is spent in protecting and managing PAs, so if this number still roughly valid, for each dollar spent in maintaining them, we would profit ~ U$60, which makes it a hell of a good deal! It is important to note that, although this study seems to be the most comprehensive representation of the global economic significance of tourism associated with PAs, the authors themselves recognize that this number is likely to be an underestimate, so the direct economic return of investing in PAs might be much higher than that!
Now, consider that the economic value of PAs is much, much, higher if we take into account the value of other ecosystem services. A recent study published by Costanza et al. 2014 shows that the global annual economic value of services provided by natural ecosystems is ~U$125 trillion. The same study shows that in less than 15 yrs, changes in land use has promoted an annual loss of U$4.3–20.2 trillion in ecosystem services. Although I could not find a global indicator of the economic participation of PAs as providers of ecosystem services, it seems an obvious conclusion that in a time where natural landscapes are being altered, destroyed and fragmented at very fast rates, PAs will have an even greater importance in protecting the natural and economic wealth of the planet.
So even under the economic development argument, one is left to wonder how governments, politicians and some other sectors of society can consider PAs a “waste of land” and endorse practices such as PADDD?! I don’t really have an answer to this question, but studies like Balmford et al. will surely help conservation biologists to make their discipline more effective and guide society to take batter informed decisions.
References
Costanza, R., et al. 2014. Changes in the global value of ecosystem services. Global Environmental Change 26: 152-158. DOI: 10.1016/j.gloenvcha.2014.04.002
Juffe-Bignoli, D., et. al. 2014. Protected Planet Report 2014. UNEP-WCMC. Available at <http://www.unep-wcmc.org/resources-and-data/protected-planet-report-2014>
Mascia, M. & Pailler, S. 2011. Protected area downgrading, downsizing, and degazettement (PADDD) and its conservation implications. Conservation Letters 4(1): 9–20. DOI: 10.1111/j.1755-263X.2010.00147.x
March 11, 2015
Why Conservation? Communicating Applied Biodiversity Science
Applied Biodiversity Science Program – Texas A&M University
You might have a favorite science writer. Mine are David Quammen, Bill Bryson, Carl Sagan, and Tim Flannery. Others may be more inclined to read Pulitzer Prize-winning and nominated authors like Jonathan Weiner, Siddhartha Mukherjee, or James Gleick, MacArthur-fellow Atul Gawande, or consummate greats like E. O. Wilson, Richard Dawkins, Stephen J. Gould, and Oliver Sacks. Or perhaps books aren’t all you’re interested in. In that case you may be a fan of Carl Zimmer’s blogging or the stories and editorials from journalists/authors Malcolm Gladwell or Stephen J. Dubner.
It’s likely you’ve read at least one of these authors. Like most readers you were probably impressed by how well they articulated the complexities and subtleties of their topic: everything from astrophysics to evolution, cancer, neurology, chaos theory, economics, and psychology. If you find an author who draws you into a topic that wouldn’t otherwise gain your attention, particularly an unfamiliar scientific discipline, take notice. Take stock of what they have accomplished by gaining your interest and curiosity. As George Gopen and Judith Swan stated in their 1990 for American Scientific, “the fundamental purpose of scientific discourse is not the mere presentation of information and thought, but rather its actual communication.” Good communication requires gaining the reader’s attention. Attention requires garnering interest and curiosity.
In our ever-connected world with vast communication and social networking ability, we have the ability to do just that. We possess the tools to communicate science to a diversity of people in a diversity of ways.
As a member of the Applied Biodiversity Science Program (ABS) at Texas A&M University I find myself in a position where communicating science is an imperative for success. The ABS program is graduate program originally funded by the National Science Foundation as part of their Integrative Graduate Education and Research Traineeship (IGERT) program. The principle mission of ABS at Texas A&M is to achieve integration between biodiversity research in the social and natural sciences with on-the-ground conservation practices and stakeholders.
To that end, a foundational component of ABS is to communicate across scientific disciplines with various institutional actors to facilitate broader impacts across the realm of conservation. In essence, the ABS Program seeks to produce applied scientists who can communicate effectively across disciplines. A natural corollary of this goal is the ability to communicate science outside the realm of science. In this respect, our ABS Perspectives Series is intended to communicate more broadly and inclusively who applied biodiversity conservationists are, what we study, where we conduct research, how we conduct research, and why we are doing it. The current issue of the ABS Perspectives Series, features experiences from the Caribbean, the United States, Sénégal, Ecuador, Nicaragua, and Costa Rica. Contributions cover topics ranging from captive parrot re-wilding with pirates to blogging in the Nicaraguan forest with limited Internet access.
Perhaps more importantly, the ABS Perspective Series wants to reach out and share ABS student and faculty experiences with a diverse readership to raise awareness of biodiversity conservation issues. Outreach is an important axiom of actionable science, especially outreach that informs, improves and influences management and policy. I consider both the ABS Perspectives Series and BioDiverse Perspectives outreach initiatives to communicate the biodiversity conservation mission to the general public, communities where our research has been conducted, fellow academics and practitioners, and institutions that can provide logistics, infrastructure, and support. We must intend to make and practice making our research accessible and intriguing to everyone.
November 18, 2014
Deconstructing Defaunation
Many species globally are threatened by numerous biotic and abiotic stressors, resulting in declining population and shifts in ecosystem functioning.
Science recently released a special issue on defaunation, which spanned seven articles detailing the recent decline in animal species diversity and abundance. Among others, the issue included two peer-reviewed articles, an opinion piece, and an analysis of national policies tied to global and local conservation strategies. The statistics associated with defaunation are sobering, but the issue presents a few solutions to help us curb this global environmental crisis.
First, a damage assessment. According to Defaunation in the Anthropocene, between 11,000 and 58,000 species go extinct each year. At least 16% of all vertebrate species are endangered or threatened, and there’s been a 28% decline in their abundances since the 1970s. Approximately 40% of invertebrate species are considered threatened, though less than 1% of described invertebrates have been assessed. There is data to suggest that invertebrate species’ abundances are also decreasing, but it’s difficult to put an exact number on that decline since they are not as well monitored as vertebrates. On a global scale, these statistics may be underestimated because our monitoring practices bias our data toward specific taxa. Groups of large and charismatic organisms, like mammals and birds, get most of the attention because they are easier to monitor and more sympathetic than invertebrates, amphibians, and reptiles. In some systems this is beneficial, where large mammals and birds are the most threatened and contribute significantly greater function to an ecosystem than smaller organisms. However the opposite can be true in other instances, so it is critical that we prioritize greater sampling of underrepresented groups.
Additionally, there is concern that such measures of declines in species and abundance may not reflect the true extent of our ecological troubles. Shifts in ecosystem compositions may not be reflected in a given measurement of biodiversity, yet are nonetheless indicative of environmental change. The primary goal behind many conservation strategies has been to restore a species or population to a certain number. While population viability is critical for any species, the authors argue that ecosystem functionality is a useful yet underutilized goal for conservationists. With this goal, the composition of an ecosystem (i.e. the identity and abundance of resident species) can be more flexible, as long as the ecosystem functions in a similar way. The issue with this then becomes how to measure ecosystem function, or rather, against what do we compare it? Do we set an arbitrary time in history that we would like to restore it to, or do we attempt to maintain its function while integrated with a unique environment managed by humans? Some proponents of the latter strategy see historical comparisons as unrealistic and uninformative, especially given our changing climate. Regardless, restoring the functionality of ecosystems is a key predictor of the future success of not only animal and plant populations, but the human population as well.
One of the strongest arguments this issue makes derives from its use of specific economic values of animals and ecosystems. According to the article Wildlife decline and social conflict, the harvest of land and sea animals accounts for $400 billion annually around the world. Defaunation in the Anthropocene claims that pest control by native U.S. predators is worth approximately $4.5 billion annually, and that the decline in North American bat populations (a specific type of pest controller) has cost the agriculture industry $22 billion in lost productivity. Insect pollinators are required for about 75% of the world’s food crops, and are therefore responsible for approximately 10% of the economic value of the entire world’s food supply. According to the World Bank, food and agriculture represents about 10% of global GDP, which in 2012 was estimated at $72 trillion. If we take total food supply to be approximately $7.2 trillion (again, estimating), then insect pollinators are worth around $72 billion dollars. These estimates apply tangible figures to a broad and occasionally overwhelming issue, and may be good starting points to unite many different stakeholders under a common currency.
The article Reversing defaunation: Restoring species in a changing world details the different strategies conservationists use to preserve species abundances and their associated ecosystem functions. These strategies can broadly be grouped into two categories, translocations and introductions. Translocations involve moving individuals within their indigenous range to either reinforce a local population or to reintroduce them following a local extinction. Introductions, on the other hand, move species outside of their indigenous range to prevent a global extinction of a species or to replace a lost ecosystem function. Though planning a conservation strategy in terms of these labels can be useful for setting long-term goals, they are not mutually exclusive. Certain strategies can incorporate aspects of both translocation and introduction, or can introduce a species both to preserve its numbers and to restore ecosystem functionality. Therefore, it’s best to use these terms as guidelines for how to measure the success of any plan rather than as constraining requirements.
These losses in biodiversity, and their associated shifts in ecosystem functioning, are primarily driven by a combination of over-hunting, habitat destruction, impacts of invasive species, climate change, and disease. The Defaunation articles make a point of addressing national policies aimed at preventing species extinctions, namely those regarding over-hunting and poaching. Many of these policies simply impose penalties for illegal hunting rather than address the underlying causes of the issue, poverty and starvation. While it’s unrealistic to expect a conservation plan to alleviate world hunger and income inequality, it may be useful to consider animal overexploitation as an unintended side-effect of the economic cycle caused by scarcity. Supply and demand states that as a species becomes less common, its value on the market rises. However, this scarcity also leads to a reduction in the amount caught per unit effort. The rise in price drives a greater hunting effort by the sellers, further decreasing the population, and the cycle begins again. Since many of these hunters are using their profits to feed themselves or their families, simply enacting penalties for poaching may not have the intended effect. Overhunting is not a simple problem, and most likely will not have a simple solution. However, the only way we can begin to address it is by determining its causes.
September 30, 2014
