Ecological time lags and the journey towards conservation success


Global conservation targets to reverse biodiversity declines and halt species extinctions are not being met despite decades of conservation action. However, a lack of measurable change in biodiversity indicators towards these targets is not necessarily a sign that conservation has failed; instead, temporal lags in species’ responses to conservation action could be masking our ability to observe progress towards conservation success. Here we present our perspective on the influence of ecological time lags on the assessment of conservation success and review the principles of time lags and their ecological drivers. We illustrate how a number of conceptual species may respond to change in a theoretical landscape and evaluate how these responses might influence our interpretation of conservation success. We then investigate a time lag in a real biodiversity indicator using empirical data and explore alternative approaches to understand the mechanisms that drive time lags. Our proposal for setting and evaluating conservation targets is to use milestones, or interim targets linked to specific ecological mechanisms at key points in time, to assess whether conservation actions are likely to be working. Accounting for ecological time lags in biodiversity targets and indicators will greatly improve the way that we evaluate conservation successes.

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Fig. 1: Habitat transformation and species–area relationships.
Fig. 2: Changes in the woodland bird index and woodland creation over time.
Fig. 3: Proportion of woodlands containing woodland bird indicator species in 2016.
Fig. 4: Bird relative abundance and species richness compared with woodland age.
Fig. 5: Schematic representing key steps in the journey towards conservation success.


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We thank all land owners who granted us permission to conduct surveys on their land, R. Whytock, P. French and P. Barbose De Andrade for assistance with data collection. This work has been developed with funding and logistical support from the Forestry Commission, University of Stirling, Natural England, Department for Environment, Food and Rural Affairs, The National Forest Company, Scottish Natural Heritage, Tarmac and the Woodland Trust. R.C.W. was funded by the Natural Research Environment Council IAPETUS Doctoral Training Partnership (grant no. NE/L002590/1) with CASE funding from Forest Research.

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K.W., K.J.P., E.F.-M. and N.A.M. conceived and designed the WrEN Project. K.W., R.C.W., N.A.M. and P.J.K.M. designed the time-lags study. K.W., R.C.W. and S.D. collated and supplied the indicator data. R.C.W. collected and analysed the bird data. K.W. and R.C.W. wrote the manuscript. All authors discussed the results and contributed to the manuscript.

Correspondence to Kevin Watts.

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Watts, K., Whytock, R.C., Park, K.J. et al. Ecological time lags and the journey towards conservation success. Nat Ecol Evol (2020).

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