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Global Biodiversity: Indicators of Recent Declines

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Science  28 May 2010:
Vol. 328, Issue 5982, pp. 1164-1168
DOI: 10.1126/science.1187512

Abstract

In 2002, world leaders committed, through the Convention on Biological Diversity, to achieve a significant reduction in the rate of biodiversity loss by 2010. We compiled 31 indicators to report on progress toward this target. Most indicators of the state of biodiversity (covering species’ population trends, extinction risk, habitat extent and condition, and community composition) showed declines, with no significant recent reductions in rate, whereas indicators of pressures on biodiversity (including resource consumption, invasive alien species, nitrogen pollution, overexploitation, and climate change impacts) showed increases. Despite some local successes and increasing responses (including extent and biodiversity coverage of protected areas, sustainable forest management, policy responses to invasive alien species, and biodiversity-related aid), the rate of biodiversity loss does not appear to be slowing.

In 2002, world leaders committed, through the Convention on Biological Diversity (CBD), “to achieve by 2010 a significant reduction of the current rate of biodiversity loss” (1), and this “2010 target” has been incorporated into the United Nations Millennium Development Goals in recognition of the impact of biodiversity loss on human well-being (2). The CBD created a framework of indicators to measure biodiversity loss at the level of genes, populations, species, and ecosystems (3, 4). Although a minority have been published individually (5), hitherto they have not been synthesized to provide an integrated outcome. Despite suggestions that the target is unlikely to be (68), or has not been (4, 9, 10), met, we test this empirically using a broad suite of biodiversity indicators.

To evaluate achievement of the 2010 target, we (i) determined the trend, and timing and direction of significant inflections in trend for individual indicators (11) and (ii) calculated aggregated indices relating to the state of biodiversity, pressures upon it, policy and management responses, and the state of benefits (ecosystem services) that people derive from biodiversity, using the best available sources. To calculate aggregate indices, we first scaled each of 24 indicators (out of 31) with available trend information to a value of 1 in the first year with data from 1970 onward (only eight indicators had earlier trends) and calculated annual proportional change from this first year. Then we used a generalized additive modeling framework (5, 12, 13) and determined significant inflections (12). Although absolute values are difficult to interpret because they aggregate different elements of biodiversity, this approach permits a synthetic interpretation of rate changes across the elements measured: For example, the aggregated state index should show positive inflections if biodiversity loss has been significantly reduced.

Our analyses suggest that biodiversity has continued to decline over the past four decades, with most (8 out of 10) state indicators showing negative trends (Fig. 1 and Table 1). There have been declines in population trends of (i) vertebrates (13) and (ii) habitat specialist birds; (iii) shorebird populations worldwide; extent of (iv) forest (14, 15); (v) mangroves; (vi) seagrass beds; and (vii) the condition of coral reefs. None show significant recent reductions in the rate of decline (Table 1), which is either fluctuating (i), stable (ii), based on too few data to test significance (iii to vi), or stable after a deceleration two decades ago (vii). Two indicators, freshwater quality and trophic integrity in the marine ecosystem, show stable and marginally improving trends, respectively, which are likely explained by geographic biases in data availability for the former and spatial expansion of fisheries for the latter (5). Aggregated trends across state indicators have declined, with no significant recent reduction in rate: The most recent inflection in the index (in 1972) was negative (Fig. 2). Because there were fewer indicators with trend data in the 1970s, we recalculated the index from 1980, which also showed accelerating biodiversity loss: The most recent inflection (2004) was negative. Finally, aggregated species’ extinction risk (i.e., biodiversity loss at the species level) has accelerated: The International Union for Conservation of Nature (IUCN) Red List Index (RLI), measuring rate of change (16, 17), shows negative trends.

Fig. 1

Indicator trends for (A) the state of biodiversity, (B) pressures upon it, (C) responses to address its loss, and (D) the benefits humans derive from it. Data scaled to 1 in 1970 (or for first year of data if >1970), modeled (if >13 data points; see Table 1), and plotted on a logarithmic ordinate axis. Shading shows 95% confidence intervals except where unavailable (i.e., mangrove, seagrass, and forest extent, nitrogen deposition, and biodiversity aid). WBI, Wild Bird Index; WPSI, Waterbird Population Status Index; LPI, Living Planet Index; RLI, Red List Index; IBA, Important Bird Area; AZE, Alliance for Zero Extinction site; IAS, invasive alien species.

Table 1

Summary of global biodiversity indicator trends.

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Fig. 2

Aggregated indices of (A) the state of biodiversity based on nine indicators of species’ population trends, habitat extent and condition, and community composition; (B) pressures on biodiversity based on five indicators of ecological footprint, nitrogen deposition, numbers of alien species, overexploitation, and climatic impacts; and (C) responses for biodiversity based on six indicators of protected area extent and biodiversity coverage, policy responses to invasive alien species, sustainable forest management, and biodiversity-related aid. Values in 1970 set to 1. Shading shows 95% confidence intervals derived from 1000 bootstraps. Significant positive/upward (open circles) and negative/downward (filled circles) inflections are indicated.

The majority of indicators of pressures on biodiversity show increasing trends over recent decades (Fig. 1 and Table 1), with increases in (i) aggregate human consumption of the planet’s ecological assets, (ii) deposition of reactive nitrogen, (iii) number of alien species in Europe, (iv) proportion of fish stocks overharvested, and (v) impact of climate change on European bird population trends (18). In no case was there a significant reduction in the rate of increase (Table 1), which was stable (i, iii, and v), fluctuating (iv), or based on too few data to test significance (ii), although growth in global nitrogen deposition may have slowed, and this may explain why the most recent inflection in aggregated trends (in 2006) was negative (Fig. 2) (5). Global trends for habitat fragmentation are unavailable, but it is probably increasing; for example, 80% of remaining Atlantic Forest fragments are <0.5 km2 in size (19), and 59% of large river systems are moderately or strongly fragmented by dams and reservoirs (20).

All indicators of policy and management responses show increasing trends (Fig. 1 and Table 1), with increases in (i) extent of protected areas (PAs) (Table 2); (ii) coverage by PAs of two subsets of Key Biodiversity Areas (21) [39% of the area of 10,993 Important Bird Areas and 42% of the area of 561 Alliance for Zero Extinction sites (22) by 2009]; (iii) area of sustainably managed forests [1.6 million km2 under Forest Stewardship Council (FSC) certification by 2007]; (iv) proportion of eligible countries signing international agreements relevant to tackling invasive alien species (IAS) [reaching 82% by 2008 (23)]; (v) proportion of countries with national legislation to control and/or limit the spread and impact of IAS [reaching 55% by 2009 (23)]; and (vi) biodiversity-related aid (reaching US$3.13 billion in 2007). The rate of increase was stable (i and iv), slowing (ii, iii, and v), or based on too few data to test significance (vi) (Table 1). The last three inflections in aggregated trends (2002, 2004, and 2008) were all negative (Fig. 2), indicating that the rate of improvement has slowed. Two other indicators have only baseline estimates: Management effectiveness was “sound” for 22% of PAs (“basic” for 65% and “clearly inadequate” for 13%), and the proportion of genetic diversity for 200 to 300 important crop species conserved ex situ in gene banks was estimated to be 70% (24).

Table 2

Examples of successes and positive trends relevant to the 2010 target (5).

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Only three indicators address trends in the benefits humans derive from biodiversity (Fig. 1 and Table 1): (i) population trends of utilized vertebrates have declined by 15% since 1970, and aggregate species’ extinction risk has increased at an accelerating rate (as shown by the RLI) for (ii) mammals, birds, and amphibian species used for food and medicine (with 23 to 36% of such species threatened with extinction) and (iii) birds that are internationally traded (principally for the pet trade; 8% threatened). Trends are not yet available for plants and other important utilized animal groups. Three other indicators, which lack trend data, show (iv) 21% of domesticated animal breeds are at risk of extinction (and 9% are already extinct); (v) languages spoken by fewer than 1000 people (22% of the current 6900 languages) have lost speakers over the past 40 years and are in danger of disappearing within this century (loss of linguistic diversity being a proxy for loss of indigenous biodiversity knowledge); and (vi) more than 100 million poor people live in remote areas within threatened ecoregions and are therefore likely to be particularly dependent upon biodiversity and the ecosystem services it provides.

Indicator development has progressed substantially since the 2010 target was set. However, there are considerable gaps and heterogeneity in geographic, taxonomic, and temporal coverage of existing indicators, with fewer data for developing countries, for nonvertebrates, and from before 1980 and after 2005 (4, 5, 25). Interlinkages between indicators and the degree to which they are representative are incompletely understood. In addition, there are gaps for several key aspects of state, pressures, responses, and especially benefits (4, 5, 7, 26).

Despite these challenges, there are sufficient data on key dimensions of biodiversity to conclude that at the global scale it is highly unlikely that the 2010 target has been met. Neither individual nor aggregated indicators of the state of biodiversity showed significant reductions in their rates of decline, apart from coral reef condition, for which there has been no further deceleration in decline since the mid-1980s. Furthermore, all pressure indicators showed increasing trends, with none significantly decelerating. Some local system-specific exceptions with positive trends for particular populations, taxa, and habitats (Table 2) suggest that, with political will and adequate resources, biodiversity loss can be reduced or reversed. More generally, individual and aggregated response indicators showed increasing trends, albeit at a decelerating rate (and with little direct information on whether such actions are effective). Overall, efforts to stem biodiversity loss have clearly been inadequate, with a growing mismatch between increasing pressures and slowing responses.

Our results show that, despite a few encouraging achievements, efforts to address the loss of biodiversity need to be substantially strengthened by reversing detrimental policies, fully integrating biodiversity into broad-scale land-use planning, incorporating its economic value adequately into decision making, and sufficiently targeting, funding and implementing policies that tackle biodiversity loss, among other measures. Sustained investment in coherent global biodiversity monitoring and indicators is essential to track and improve the effectiveness of these responses.

Supporting Online Material

www.sciencemag.org/cgi/content/full/science.1187512/DC1

Methods

SOM Text

Figs. S1 and S2

Tables S1 to S4

References

Data File 1

References and Notes

  1. Further information is available as supporting material on Science Online.
  2. We are grateful for comments, data, or help from R. Akçakaya, L. Alvarez-Filip, A. Angulo, L. Bennun, L. Coad, N. Cox, M. Dubé, C. Estreguil, M. Evans, B. Galil, V. Gaveau, F. Gherardi, S. Goldfinger, R. Green, A. Grigg, P. Herkenrath, C. Hilton-Taylor, M. Hoffmann, E. Kleynhans, J. Lamoreux, S. Livingstone, E. Marais, P. Martin, I. May, A. Milam, K. Noonan-Mooney, H. Pavese, B. Polidoro, C. Pollock, D. Pritchard, J. Schipper, F. Schutyser, V. Shutte, S. Simons, J. Škorpilová, A. Stattersfield, P. Voříšek, R. Wright, M. Wackernagel, and M. Waycott. We acknowledge support from the Global Environment Facility to the 2010 Biodiversity Indicators Partnership; Shell Foundation; European Commission; the Sea Around Us Project (University of British Columbia/Pew Environment Group) to D.P. and R.W.; World Wildlife Fund, The Nature Conservancy, and the University of Queensland to M.H. and F.L.; T. Haas and the New Hampshire Charitable Foundation to K.E.C.; and the National Science Foundation (NSF) to J.-F.L. Opinions and findings expressed here do not necessarily reflect the views of the NSF or other funding bodies.
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