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. Ecological time-lags and conservation success

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1. Agricultural intensification and expansion are regarded as major causes of worldwide declines in biodiversity during the last century. Agri-environment schemes (AES) have been introduced in many countries as an attempt to counteract the negative effects of intensive agriculture by providing financial incentives for farmers to adopt environmentally-sensitive agricultural practices. 2. We surveyed 18 pairs of AES and conventionally-managed farms in central Scotland (United Kingdom) to evaluate the effects of specific AES management prescriptions (field margins, hedgerows, species-rich grasslands and water margins) on farmland moths. We also measured the influence of the surrounding landscape on moth populations at three spatial scales (250 m, 500 m and 1 km radii from each trapping site) to assess at which scale management was most important for the conservation of farmland moths. 3. In general, percentage cover of rough grassland and scrub within 250 m of the trapping site was the most important landscape predictor for both micro-and macromoth abundance and macromoth species richness, although negative effects of urbanization were found at wider scales (within 1 km), particularly for macromoth species richness. 4. The abundance and species richness of micromoths was significantly higher within field margins and species-rich grasslands under AES management in comparison to their conventional counterparts, whereas AES water margins increased micromoth abundance, but not species richness. AES species-rich grasslands and water margins were associated with an increased macromoth abundance and species richness, and macromoths considered 'widespread but rapidly declining' also gained some benefits from these two AES prescriptions. In contrast, hedgerows under AES management enhanced neither micromoth nor macromoth populations. 5. Synthesis and applications. Our findings indicate that increasing the percentage cover of semi-natural environment at a local scale (e.g. within 250 m) benefits both micro-and macromoth populations, and that the implementation of simple AES management prescriptions applied to relatively small areas can increase the species richness and abundance of moth populations in agricultural environments.

The development of ecological networks could help reverse the effects of habitat fragmentation on woodland biodiversity in temperate agricultural landscapes. However, efforts to create networks need to be underpinned by clear evidence of the relative efficacy of local (e.g. improving or expanding existing habitat patches) versus landscape-scale actions (e.g. creating new habitat or corridors in the landscape matrix). Using cluster analyses we synthesised the findings of 104 studies, published between 1990 and 2013 focusing on the responses of woodland vascular plant, vertebrate, cryptogam and invertebrate species to local and landscape variables. Species responses (richness, diversity, occurrence) were strongly influenced by patch area, patch characteristics (e.g. stand structure) and isolation (e.g. distance between habitat patches). Patch characteristics were of overriding importance for all species groups, especially cryptogams. Many studies recording significant species responses to patch characteristics did not record significant responses to patch area and vice versa, suggesting that patch area may sometimes act as a surrogate for patch characteristics (i.e. larger patches being of ‘better quality’). Ecological continuity was important for vascular plants, but assessed in only a few vertebrate and invertebrate studies. Matrix structure (e.g. presence of corridors) was important for vertebrates, but rarely assessed for other species groups. Actions to develop ecological networks should focus on enhancing the quality and/or size of existing habitat patches and reducing isolation between patches. However, given that very few studies have assessed all local and landscape variables together, further information on the relative impacts of different attributes of ecological networks in temperate agricultural landscapes is urgently needed

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