Suppose that a disinterested Martian scientist heard about the 2010 target and offered its services as a consultant to advise our species on how to set up an appropriate monitoring system. The Martian might begin by asking us why we are concerned about the loss of nature and what our purpose is in monitoring it.
Representatives of our species would presumably reply that they are worried about the extent to which their actions are causing the loss of things derived from biodiversity, not only as they affect their own interests as individuals, but also as they affect the interests of other people with no power or formal representation, such as children, future generations, and those with little political or economic influence. People might also say that they are ethically disquieted about the destruction they are inflicting on other species, including those that they do not think of as having any value. The answer about the purpose of the monitoring would be that it is to quantify the loss of wild nature, while establishing the extent to which actions taken to reduce that loss are being successful.
Before advising on the design of the monitoring programme, the Martian would ask for more information on our understanding of the nature, origins, magnitude and distribution of the benefits that we derive from biodiversity. It would immediately be obvious that the benefits are diverse. They include provisioning benefits, in particular food, fibres, water, pharmaceuticals and other goods obtained from wild ecosystems; regulating benefits, such as controls exerted by ecosystems on climate, disease, fire and flood; supporting benefits, such as nutrient cycling and the pollination of crops; and cultural benefits derived from the appreciation and enjoyment of nature. Some of these benefits are spread widely across many people, while others are enjoyed only by particular groups. It would also be evident that many benefits involve long-distance connections, so that the beneficiaries may not live near the resource providing the benefit. A marine fishery may depend on the existence of intertidal habitats for young fishes hundreds of kilometres away, and the food and financial benefits it provides may accrue to people living hundreds or thousands of kilometres away. The Martian would conclude that, partly as a result of this diversity and complexity, the benefits derived from biodiversity are large but mostly not well quantified, and that our understanding of the mechanisms linking the delivery of these benefits to the state of ecosystems, the abundance of their component species, and internal and external drivers of change, is crude at best.
Arguing from the viewpoint that it is unwise to discard parts of a mechanism whose function and importance you do not understand, the Martian would advise that it would be unsafe to focus monitoring exclusively on a few aspects of biodiversity that we perceive to be delivering many benefits (though these should certainly be covered). Measurements should instead be made of a wide range of attributes of wild nature, including (i) the population size and risk of extinction of species, (ii) the extent and condition of habitats and (iii) the rate of delivery of benefits. In addition, the Martian would advise that, because one purpose of the monitoring is to assess whether action to achieve the target is succeeding, measurements should also be made of (iv) drivers that cause biodiversity loss, such as habitat conversion and overexploitation of wild species; and of (v) activities undertaken to conserve biodiversity, such as protected areas (PAs) and programmes for sustainable resource use. In many cases, measurement would concentrate on unconverted habitats, free-ranging populations, or the services they provide, but in more transformed parts of the planet wild species living on farmland or even races of domesticated species could be legitimate subjects for monitoring.
Having suggested what kinds of attributes ought to be measured, the Martian would give some guidance on how to carry out the measurements. The advice would be that the methods chosen should be practical given the time and resources available, and accurate and precise enough for the purpose. Answers are required quickly and resources are limited. Therefore, sampling, rather than measuring every population or the total extent of every habitat, would be recommended in most cases. If estimates based upon samples are to be accurate, the sample of species or locations must be representative of the whole—geographically, taxonomically, across habitat types, and across levels of threat or degradation. The precision of the estimates will be driven by the size and stratification of the sample and should be decided based on how the results will be used for decision-making and the cost of each sample; it might be sensible to direct disproportionate sampling effort towards components likely to be of most importance in terms of benefit delivery, those that are richest in biodiversity, and those that are changing fastest. Composite indicators derived from combined data from many areas or species should be based on data that can be disaggregated to examine their components and recombined into different groupings. Measurements should be carried out in a standardized way that can be repeated comparably later and by other people, and the assumptions and uncertainties in measurement protocols must be made explicit. Measurements should be repeated on several occasions to measure trends over time. The CBD target calls for a reduction in the rate of biodiversity loss, which would require us to have a minimum of three measurements by 2010. However, if short-term fluctuations occur or the measurements are imprecise, many more sampling occasions may be needed. The Martian would recommend pilot studies and inputs to programme design by statisticians to optimize the estimation of trends.
The Martian would also argue that because people do not yet know enough about their planet and its biota, the monitoring system must be adaptive and capable of shedding light on how management actions can best reduce the loss of biodiversity. Monitoring must therefore be based around a set of competing provisional models of the system, each of which makes explicit the linkages between its components and identifies the levers that decision-makers can use to deliver desired changes. Each model can be used to make predictions about the consequences of different courses of action. Monitoring should be designed to reveal whether or not the expected outcomes actually happen. Several plausible (and some not so plausible) variants of the model should exist and the monitoring results should be compared with the predictions of all of them. The models should compete to satisfy our demands for understanding and utility. The Martian would note the similarity of this process to one of our species' great triumphs of understanding, the theory of evolution by natural selection.
Who should fund this programme? The Martian would suggest it should perhaps be those who would derive most benefit from it. If the programme helps protect biodiversity then many species would benefit. But among the human species there seems to be a constant tension between the subspecies who extract resources from the environment and the subspecies trying to protect and monitor it. These interactions frequently lead to punitive retrospective legal cases which seem mainly to benefit a third, largely parasitic subspecies of humans. Surely it might be better if the monitoring could be done as some form of collaboration between the extractive and the protective subspecies. The extractive group seems to have significant resources to devote to the task and much to benefit from knowing the current and future impact of their activities. The broader alliances that might develop between these two groups might even allow them to modify or overrule the decisions of the largely parasitic subspecies, who currently seem to dominate the decision-making processes.
The Martian might also advise us to expect the real returns from actions and monitoring to accrue over a longer period than the next five years. Among these will be a better appreciation of what our targets should be. Merely reducing the rate of loss of biodiversity is unlikely to be what we really want. Reducing the rate of decline of the global population of a plant or animal species, for example, would delay, but not prevent, its extinction. Likewise, preventing further decline and even allowing modest recovery of a seriously depleted fish stock might not be sufficient to allow sustainable exploitation, even over the medium term. Instead, improved understanding is likely to lead away from a focus on slowing negative trends to the identification of targets for restoring important components of the Earth system to desired states different from those of recent decades.
In writing its report, the Martian supposes that all of this advice is pretty obvious, but just before leaving thinks it would be sensible to check that we are indeed collecting robust data on the biomes and taxonomic groups that include the greatest variety of our fellow life-forms and that supply the most valuable and irreplaceable services. Disappointingly, it appears instead that we are concentrating our monitoring efforts on species which most closely resemble ourselves, in places where people with the most money and spare time happen to live. In the final recommendation of its report, the Martian therefore tactfully suggests that we might want to review what, where and how we are monitoring, and what the weaknesses and gaps in our measurements and understanding are, in case there is any room for improvement.