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Global Homogenization, Invasives and the Conservancy’s Mission

Lowenstein, Frank 9/13/2011

The crisis of environmental degradation has progressed to the point of impacting evolutionary processes and outcomes on geologic time frames (Ehrlich and Pringle 2008; Mooney and Cleland 2001; Myers and Knoll 2001). The components of this degradation are sometimes collectively characterized as “global change” (Sala et al 2000), including:

  • Global climate change and direct effects of rising carbon dioxide levels;
  • Changes in other global biogeochemical cycles, particularly nitrogen enrichment;
  • Movement of organisms worldwide; and
  • Changes in global land-use patterns.

These changes are rapidly reshuffling the evolutionary deck and driving ever faster change in natural systems. For The Nature Conservancy, these dynamics present a significant mission challenge that is not yet fully recognized in our conservation thinking, actions, strategies and planning. And that challenge also requires a rethinking of how we address invasive species.

Rate of Species Creation and the Threat of Invasives and Homogenization to TNC’s Mission
The nascent science addressing novel ecosystems (Hobbs et al. 2006, Lindenmayer et al. 2008, Seastedt et al. 2008) tries to grapple with appropriate conservation goals for our human-dominated world. This work correctly identifies that the past composition and structure of ecosystems is a poor guide for future management. For example, we are in a period of exceptionally rapid and accelerating climate change. Paleoecological studies show that during the last period of major climate change — following the end of the last glaciation — plant communities were radically unstable (Schoonmaker and Foster 1991). For example, different tree species responded individually and in dramatically different ways to changing climate. Community compositions that existed then may not exist anywhere today, and vice versa.

So, if the community compositions we see today are ephemeral responses to underlying conditions, and those conditions will change dramatically over the next decades, why should we worry about community composition, invasive species or any other aspect of which species is found where?

The answer is that invasive species are symptomatic of the one aspect of global change (Sala et al 2000) that most directly undermines TNC's conservation approach. Non-native and invasive species matter not only at the community level, but also at the level of biogeographic realms. Global biodiversity derives from evolution acting on separate assemblages of species. Darwin’s finches on the Galapagos Islands, the diversity of marsupial life in Australia, and the unique fynbos flora of South Africa are all startling examples of how evolution can produce remarkable life histories and life forms given a long-enough geographic separation. Even if species shift around within a large region (think Australia), evolution still operates on the same pool of species.

The Conservancy’s conservation approach relies on ensuring the survival of the representative examples of the biotas of the many regions we work in. As a strategy to preserve global biodiversity, the success of such a representation approach relies on the existence of differences in biota derived from evolution operating over time — so that landscapes we work on in China result in the conservation of different species than we achieve via working in Argentina or Pennsylvania.

Today, homogenization via enhanced global movement of species is reducing the number of separate lineages of flora and fauna subject to evolution. Biogeographic barriers like the Bering Strait, the Pacific Ocean and the Isthmus of Panama are breached routinely and daily through unintentional hitchhikers on the planes and ships engaged in global trade, through intentional introductions for agriculture and horticulture, and via species carried with migrating humans for food or pleasure. And the pace of this exchange is accelerating (Levine and D’Antonio 2003, Westphal et al. 2008).

The ultimate effect is likely to be a reduction in the rate of creation of new species. This threat is entirely separate from the threat to biodiversity that TNC and many conservation biologists tend to focus on — accelerated rates of extinction — but it makes the impact of that second threat more dire (Myers and Knoll 2001). In addition, global loss of specialist species due to habitat disruption, global environmental changes such as climate change, and breakdown in biogeographic barriers could result in loss of ecosystem resiliency and the ecosystem services that people rely upon (Clavel et al 2011). When introduced to a new biogeographic realm, some but not all introduced organisms become widespread in natural areas and may reduce biodiversity as a result, either by competing with native species, by eating native species, or by changing underlying ecosystem processes. Destructive, aggressively spreading non-native species are labeled as invasives, and are often identified as key threats to biodiversity at the site or system level.

Is the Conservancy Focusing on the Symptom, But Missing the Disease?
In response to these kinds of threat assessments, our organization has invested deeply in invasives control and encouraged partners to do the same. Dozens if not hundreds of TNC staff in the organization’s U.S. operating units have invasives control as part of their portfolios. These investments are often necessary, as at their worst invasive species can be game changers. For example, two species of invasive plants may bring East Africa’s vast migratory herds to a halt (Witt 2011).

But by focusing on invasive species primarily once they manifest as a threat at a given place, the Conservancy is masking the more subtle and ultimately more troublesome source of this stress — the homogenization of the global biota. By focusing on the symptom, we have missed the disease, and produced a misallocation of resources, with operating units desperately trying to abate threats at the site or system level, while at the global level we now lack any capacity to address the policies that degrade the uniqueness and diversity of entire biogeographic realms. The North America CR Forest Health Protection Program does still work at the U.S. national level to prevent introduction and spread of one category of potential invaders, and some Conservancy operating units (e.g., Florida) have integrated invasives management efforts that extend from the site level to state policy. But since the demise of TNC’s Global Invasive Species Team, we have had little organizational voice addressing the movement of biota across the globe or reinforcing these efforts at the national level in the United States or beyond.

Today’s most severe threats to biodiversity — derived from continued excessive use of fossil fuels, globalization of trade, and growth in human population and individual consumption — affect many places at once. These threats are not amenable to local solutions acting in isolation, and they require a sustained commitment over long time scales to achieve strategy success.

What the Conservancy Needs to Do to Respond to These New Threats
We need a planning process that builds consensus for action to address these threats across multiple operating units, incorporates longer time scales, recognizes the dominant place of people in controlling and managing the forces that limit and shape biodiversity today, and ensures that evolutionary processes essential to TNC's mission success continue to operate.

TNC’s new Global Challenges/Global Solutions (GCGS) framework begins to address the critical role of people in the future of biodiversity, but it is not yet integrated into the planning processes that guide most of our organization’s day-to-day work. To build on the GCGS framework and make it real in the context of the threats mentioned above, we need a number of changes:

First, we need to ensure that our planning routinely evaluates not only threats to multiple conservation targets at a single site, but also 1) threats to a single target at multiple sites and 2) strategies to abate a single threat to multiple targets at multiple sites. Such broadening of our planning scope will allow us to focus on higher leverage strategies capable of benefiting multiple sites simultaneously.

Second, we need to address threats more proactively. The 10-year timeline commonly used in conservation-area planning steers our efforts strongly to imminent threats that are usually already severely damaging conservation targets. But longer-term threats often can be abated only through action well ahead of time. For example, invasive species strategies aiming to prevent future homogenization and associated invasion will rank low in our planning priorities because they do not likely address threats within the next 10 years. Climate change and atmospheric nitrogen enrichment are subject to similar time-frame ranking problems, and yet require actions across decades to abate the threat.

Third, the ranking of scope within our Conservation Action Planning results in the misrating of those threats that can be prevented only through early action. For example, the literature is clear that invasive species eradication efforts succeed best when attempted early in an invasion, when the geographic scale of the infestation is tiny (Simberloff 2003). But tiny infestations have minuscule scope, and may spread slowly enough that, even after 10 years, they will still rank low in scope. The focus on threats already affecting much of a conservation target impedes a proactive, preventative approach to invasives and many other issues.

Finally, TNC needs a framework for dealing with a host of novel conservation issues — such as our response to genetically modified organisms intended for introduction to natural areas (e.g. genetically modified American chestnuts); how to build on our expertise in conserving biodiversity in working landscapes to cope with the spread of entirely novel habitats; and what to do about native species that begin to behave like invasive organisms due to climate change or altered ecosystem structure.

Beyond these changes to our planning efforts, we need difficult changes in our own organization. Operating units must overcome their mistrust of central programs and recognize that common action is essential to abate the underlying cause of common threats. Implementing this recognition will require more of some difficult tasks that many operating units already undertake: specifically it will require fundraising and leadership staff to successfully make the case for funding programs beyond their geography (including at the regional and global level), even at the expense of the growth of local efforts. And global programs must be held to standards of effectiveness so that operating units know their funds are well spent.

As to invasives, their threat did not decrease with the foundering of the Global Invasive Species Team, and the homogenization of the Earth’s biota continues unabated, sowing the seeds literally and figuratively of tomorrow’s invasives threats. Concerted action at the national and global levels can function to reduce the flow of species, and eventually I believe the Conservancy will again recognize the need for a global approach. But there are many ways to provide for unified action. Perhaps we will address the spread of organisms as one aspect of a team that tackles a range of traderelated conservation issues, such as illegal logging and its impacts on forest ecosystems, and the tradeoffs between biofuels, agriculture and poverty. Time will tell. All that is certain is that, in the case of invasives, the threat — symptom and disease — remains. Ignoring it, or claiming that its import is reduced in a time of novel ecosystems, ignores the role of evolution and history in our organization’s future success.

Author’s Note: During my nearly 19 years at the Conservancy, I have worked at the site, division, regional and global levels — but for the last several years I have worked almost exclusively at the national to global level, including on the issues of invasive species, trade and (most recently) global climate change. The latter experience may be influencing my thinking!

Acknowledgements: Many thanks to D. Gordon, F. Campbell, R. Lalasz, T. Weldy, M. Jordan and K. Serbesoff-King for useful comments on this manuscript and suggestions of relevant articles, and to John Randall and a host of other colleagues for many conversations and ideas that have helped to shape my conservation thinking.

Clavel, J., R. Julliard and V. Devictor. 2011. Worldwide decline of specialist species: Toward a global functional homogenization? Frontiers 9(4):222-228

Ehrlich, P.R., and R.M. Pringle. 2008. Where does biodiversity go from here? A grim business-as-usual forecast and a hopeful portfolio of partial solutions. PNAS 105:11579-11586

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Image: Flowers in South Africa’s fynbos. Image credit: Paul Perton/Flickr.