over the target amount?
Josie Carwardine, Science Alert 28 Oct 09;
Lots of decisions in life are based on targets, and conservation is no exception. When we want to decide how to invest in saving biodiversity, we set targets like how many populations of each species should be protected in a reserve system; or how many hectares of each vegetation type we should protect from cattle grazing? These targets help to control how we divide our efforts amongst all the features of biodiversity that we care about, and provide us with a benchmark for measuring our achievements.
But can setting a target have bad impacts for biodiversity? Some scientists and conservationists argue that targets give society a license to destroy the proportions of species and habitats that are above a target amount (eg, Soulé & Sanjayan 1998, Woinarski et al. 2007).
So if we set a goal of protecting 30 per cent of each vegetation type, does this mean 70 per cent of it can be destroyed? And to make matters worse, is 30 per cent protected enough to make a difference – is it enough to sustain a species in the first place?
I work in the area of spatial priority setting, and targets are part and parcel of the conservation planning I’m involved in. To me, target-based conservation planning seems like a sensible, practical and transparent approach to protecting biodiversity, but I know it is important to understand the potential limitations of the approach you are working with. Consequently I’m very interested in understanding the strengths and weaknesses of targets as a means of securing the conservation of our precious biodiversity.
Over the last year I’ve been discussing the perceived problems with conservation targets with a group of AEDA researchers including Carissa Klein, Hugh Possingham, Bob Pressey and Kerrie Wilson, and the results of our discussions are now presented in the journal Conservation Letters (Carwardine et al, 2009). In this paper we argue that targets are actually good for conservation, but our communication of them could do with some serious improvement. So, if you’ve ever been in a debate where the value of conservation targets was under question, it wouldn’t hurt to be familiar with the arguments.
Six common concerns
We found six commonly reported ‘limitations’ of targets in conservation planning:
1. setting conservation targets results in perverse outcomes;
2. conservation plans based on targets will be inadequate;
3. conservation plans based on targets will be inflexible and over-ride expert judgement;
4. conservation plans based on targets will be unachievable;
5. the approach fails in intact landscapes; and
6. the approach cannot consider complex factors such as climate change, ecological processes, threats and socioeconomic criteria.
We came to the conclusion that most of these concerns are misconceived, and have arisen from poor communication about the nature and intentions of conservation targets. Consider for example:
1. The concern that targets give license to destroy the untargeted proportions of a feature has arisen through confusion about the role of conservation targets.
Conservation targets are often used to protect minimum amounts of each biodiversity feature in a reserve (eg, Commonwealth of Australia 2005), but they actually say nothing about the remainder of the landscape. Regardless of reserve selection approach, the fate of biodiversity outside reserves must be protected by clearing laws and policies, fishery quotas, and best-practice farming. It is a perverse interpretation of conservation targets to suggest they give license to destroy biodiversity - a bit like saying that nobody should get more than the minimum wage!
2. Concerns that target amounts are inadequate have arisen because we haven’t articulated clearly that targets are sometimes defined by socio-political feasibility, rather than by persistence requirements.
The purpose of socio-political targets – such as protecting 10 per cent to 30 per cent of the historical extent of major vegetation types as recommended by the World Conservation Union – is to ensure equity of protection, where previously ecosystems with value for productive or extraction were overlooked. More “adequate” targets are often set by accounting for factors that affect species persistence. Scientists need to communicate that both types of targets are adaptive, and can be revised with increased biological knowledge and changing social and ecological conditions.
3. We need to make it clearer that the quantitative phase of conservation planning is only one part of the process, so areas known to be important can be picked up by experts.
It is best practice for all quantitative conservation planning tools to be used in conjunction with expert knowledge and intuition, because many elements of biodiversity and socio-ecological systems cannot be captured with available data. Many people have probably been misled on this point because academic examples target-based planning often don’t involve expert input.
4. Ambitious targets are used to represent longerterm objectives in the face of short-term constraints, so it is OK if targets cannot all be achieved at once.
Due to a lack of resources, targets are often unachievable in the short term, but they are useful for influencing policy by highlighting current funding shortfalls. Conservation actions for meeting targets can be scheduled over time, using factors like irreplaceability and threat. While knowledge of the potential availability of conservation areas should be investigated prior to planning to determine the appropriate kinds of conservation actions, maps of the relative importance of areas for meeting targets can help determine whether to carry out an action (eg, purchase for a reserve) in an area if it becomes available in the future.
5. Target-based conservation planning is flexible and can work in all landscapes.
Target-based conservation planning has been used successfully for both intact and fragmented landscapes in both the land and sea. For example, the intact Great Barrier Marine Park was re-zoned using a target-based approach. However, targets may have different implications in different landscapes: In fragmented landscapes most remaining areas of remnant ecosystem plus some restoration may be needed to achieve targets, while in intact landscapes there is more flexibility and scope for accommodating larger targets, biodiversity processes and off-reserve actions.
6. Target-based conservation planning is not limited by complex factors more than by our ability to define and parameterise them.
The concern that target-based conservation planning cannot address complex factors has arisen because developments of the approach are not widely disseminated. Target-based conservation planning is continually evolving to address complex factors such as off-reserve conservation, multiple actions and benefits, ecological processes, climate change, threats, condition, dynamics and socio-economic issues. The main challenges are not in the development of new algorithms, but in defining the problem mathematically and parameterising it with relevant data.
Are there alternatives to target-based conservation planning?
Many proposed alternatives to target-based conservation planning do not solve any kind of quantifiable objective (something that is being maximised or minimised). For example the guiding principles laid out in Woinarski et al. (2007) in their discussion on the conservation of Australia’s north are:
1. The natural environments must be valued recognizing their national and international significance
2. The ecological integrity of the processes that support life must be maintained
3. The population viability of all native species must be protected
4. Thresholds defined by the limits to ecological integrity must be used to assess and guide development options
5. The contributions of all property holders and managers are needed to maintain the North’s natural values.
These are excellent principles for informing quantitative approaches. However, by themselves they are not enough to determine where, when and how to manage for conservation.
Targets are not the only quantitative way to prioritise conservation efforts over multiple biodiversity features. Alternative approaches include maximal covering problems, where the objective is to maximise the utility, or benefit, gained by spending a fixed budget. Figure 1 shows the different ways that target-based and non-target based problems measure the utility of protecting increasing amounts of a feature (Figure 1, Lines A-E).
Continuous utility functions have more biological meaning than target-based utility functions, but targets have some practical advantages for planners and policy-makers. They are simple to convey, politically tractable, and allow whole portfolios of potential conservation areas to be identified.
Most importantly, they provide a clear goal – many conservation planners need to know when their short-term goals have been achieved.
Figure 1: Target-based and alternative utility functions for a single vegetation type. The utility indicates the benefit of protecting increasing amounts of a single vegetation type. In simple target-based approaches, benefit is zero until the entire target – in this case 30 per cent of the extent of the vegetation type – is reached (A). Alternatively, utility is gained incrementally until the target is reached (B). In both A and B no utility is gained beyond the target amount. In continuous (non-target) utility functions some additional benefit is gained from each incremental area protected. The shape can be linear (C), where utility accrues in equal increments until the entire vegetation type is conserved, or can follow diminishing returns (D) or sigmoidal (E) curves.
More info: j.carwardine@qu.edu.auThis e-mail address is being protected from spam bots, you need JavaScript enabled to view it
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References
Carwardine J, CJ Klein, HP Possingham, RL Pressey, & KA Wilson (2009). Hitting the target and missing the point: conservation targets in context. Conservation Letters 2, 4-11.
Commonwealth of Australia (2005). Direction for the Australian National Reserve System
Soulé E & MA Sanjayan (1998). Conservation targets: do they help? Science 279, 2060-2061.
Woinarski J, B Mackey, H Nix, & BJ Traill (2007). The Nature of Northern Australia: its natural values, ecology, and future prospects. ANU Electronic Press, Canberra.