Key Context

This report is required for Kew’s Operational Plan Review (OPR) performance metrics. For more information on methodologies and wider context see Cano et al. (2025).

Transience in living collections is the most important concept to apply when interpreting these analyses.
A plant alive one day can be dead the next, and at this point is no longer present in the collection.
If that plant was the only individual of its species in the collections, then the species is also now absent, whereas the day prior it was present.
Put simply, failure to regularly report whether living collections are ‘Alive’ or ‘Dead’ leads to wildly inaccurate figures, and this is more frequently encountered scenario in the worlds 3,500 botanic gardens. The frequency of reporting can be thought of as ‘data health’.
These data are only ever a proxy for the real picture, where low data health can produce overinflated numbers, and increasing data health is often represented on longitudinal charts as a loss of diversity. What is actually occurring in these instances is correction of overstated figures.

Key Dates:

1983: National Heritage Act states RBGK held 45,000 species in living plant collections. The authors of this report consider this figure a overestimation, likely generated through counting paper records with no way of applying a reference taxonomy.
1992: First digital catalogue editable on site was installed. This point aligns with peak diversity reported, but also correlates with the move from paper to digital records. Records that were already ‘Dead’ pre-1992 were never digitised, rendering a full digital picture impossible.
2019: Living Collections Strategy published
2020: New database procured, site wide audits commenced.
2023: Audit completed at Kew site and all living collections confirmed present marked ‘Alive’ and records with no corresponding plants marked ‘Dead’.
2025: the living collections database was integrated with the science collections into the integrated collections management system (ICMS), further improving systems.

1. Diversity Metrics

OPR Target: There are no OPR targets for diversity, but it is a useful barometer.

These charts explore the recorded diversity of Kew’s living collections over time by calculating how many plants were alive in a given year and then grouping those by species and taxa.

1.1 Species and taxa counts over time

The first chart looks at absolute values for species and taxa alive in the collections over the last 20 years. ‘Species’ here means all accepted scientific names with taxonomic rank ‘species’, so all lower ranks are filtered out. ‘Taxa’ includes all infraspecific taxa but all cultivated taxa (cultivars and experimental hybrids) are filtered out. ‘These trends should be considered alongside ’average days since last seen’ in data health metrics in section 5 for context. ‘Stock checks completed’ shows total number of stock checks recorded. A negative diversity trend which correlates with improved data accuracy indicates that the apparent decline may be due to better collection management rather than loss of plants, a gradual correction of an overinflated figure.

Year	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023	2024	2025	2026
Species	21410	21303	21106	20927	20092	19909	19684	19602	19506	19341	19248	18998	18792	18580	18451	18469	18048	17405	16916	16860	16547
Taxa	30708	30645	30354	30418	29370	29178	28872	28702	28594	28475	28396	27983	27725	27446	27167	27179	26547	25514	24932	24746	24137

1.2 All ranks normalised

The second chart includes families, genera and cultivated taxa on one axis, but expresses them as normalised (% of the maximum for the given timeframe) values over the last 20 years. Stock checks are again shown on the second axis in absolute values. Cultivated taxa here refers to plants with horticultural nomenclature, mainly cultivars and experimental hybrids. Plotting absolute numbers for these groups is not instructive as the range and variance within each series are not directly comparable. Cultivated taxa here are the only group that go against the generally decreasing trend, indicating that from 2008 to 2016 a large amount of cultivated taxa were brought into the living collections. These taxa often (but not always) have fewer research and conservation applications and are available in the horticultural trade.

Year	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023	2024	2025	2026
Species	21410	21303	21106	20927	20092	19909	19684	19602	19506	19341	19248	18998	18792	18580	18451	18469	18048	17405	16916	16860	16547
Taxa	30708	30645	30354	30418	29370	29178	28872	28702	28594	28475	28396	27983	27725	27446	27167	27179	26547	25514	24932	24746	24137
Genera	4329	4333	4301	4268	4176	4138	4078	4074	4049	4018	4001	3954	3930	3904	3878	3851	3804	3682	3604	3567	3541
Families	333	333	334	334	333	334	333	332	332	331	337	336	336	333	332	330	329	324	319	317	317
Cultivated	5923	5979	5951	6243	6175	6209	6166	6111	6130	6198	6231	6122	6099	6073	5952	5966	5832	5544	5563	5467	5244

2. Conservation Metrics

OPR Target: 3% increase year on year. 2025 actuals: 2026 target:

2.1 Presence of IUCN threatened taxa over time

The next set of charts look at the presence of IUCN threatened taxa over time, aiming for 3% growth year on year. IUCN publish new red lists annually and the most recent red list (2025-1) is used for each year retrospectively in this analysis. The downward trend, as before, can be explained by increased quality of collections management, correcting overinflated figures. An increase of 3% of threatened taxa in collections (equivalent to 40 new taxa for 2025, exponentially increasing, acquired and fully established) per year may be an unrealistic target, and has only been achieved once in the timeframe examined, notwithstanding doubts around accuracy of this figures. Ex situ conservation in living collections is not driven purely by quantity; it should be considered alongside other quality metrics for a better assessment of impact.

Year	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023	2024	2025	2026
IUCN threatened taxa	1471	1493	1522	1519	1470	1461	1447	1446	1457	1459	1455	1445	1439	1421	1429	1445	1437	1412	1363	1371	1352

2.2 Presence of IUCN threatened taxa over time (normalised and categorical)

This next plot is normalised and shows the movement over the same period relative to the highest total for each series over the last 20 years. We consider ‘threatened’ to mean assessment values of any of the following: VU = Vulnerable, EN = Endangered, CR = Critically Endangered and EW = Extinct in the Wild. The negative trends can once more be explained by increasing data health. The positive trend of EW plants can either mean we have acquired plant material listed as EW, or material we already had has been formally assessed as EW in the last few years.

Year	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023	2024	2025	2026
CR	289	291	300	300	299	302	297	296	298	296	296	297	294	281	284	288	290	287	279	284	281
EN	560	572	588	589	567	556	550	551	558	563	563	556	555	550	555	563	558	550	532	531	515
EW	20	20	20	19	19	19	19	19	19	21	21	21	21	21	21	21	21	21	22	22	22
VU	600	608	612	609	583	582	579	578	580	577	573	569	567	568	568	572	567	553	529	532	532

3. Utilisation Metrics

OPR Target: 500 plants sampled for science or donated to other institutions per year.

3.1 Samples and orders fulfilled

These charts show the use of living collections in research, conservation or supply to other institutions. It is split into count of individual plant parts or whole plants taken (samples or donations) and count of ‘orders’ facilitated (orders fulfilled). One order often contains many individual samples. Samples can include whole plants, cuttings or other plant parts. Orders fulfilled can be internal or external. Our OPR target is 500 individual samples or donations per year.

Year	2022	2023	2024	2025	2026
Samples or donations	698	1740	603	1122	1165
Orders fulfilled	74	55	48	91	78

4. Wild Accession Metrics

OPR Target: >300 per year

4.1 New wild source introductions over time (unique wild accessions vs. total wild accessions)

New wild-source accessions into the living collections are critical to Kew’s mission. They contain the highest value for research and conservation and often yield the greatest stories. Examining in influx of ‘high-quality’ material can reveal trends in our acquisition behaviour.

Pre-2020, Kew’s data systems and processes duplicated accessions. This masked the true number of unique wild-source accessions, which was lower than claimed. Large peaks are down to expeditions executed in a give year, and troughs due to lack of activity. The gentle recent increase is likely stronger due to several hundred pending high value accessions have yet to enter the system from work in 2025 and 2026.

Year	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023	2024	2025	2026
Accessions	1138	876	1290	1115	714	521	452	554	1064	1036	1086	970	713	1108	683	666	252	450	360	755	266
Distinct accessions	417	219	464	427	182	156	151	239	556	619	390	220	195	263	294	407	129	277	241	460	221

5. Data Health Metrics

OPR Target: Less than 10% of living collections inspections overdue

5.1 Average days since last stock check, absolute counts of material in and out per year

Living plants die in botanical collections. Gaps in recording mean these records stay as living, meaning assessments of diversity are overstated and sample provisions can’t be fulfilled. Good collection management signatures can be drawn out of living collections data.

This chart shows an assessment of data health, represented by the blue trendline. The columns show the absolute numbers of objects in and objects out. This is measuring the average days since the living collections were last confirmed alive. A rising blue line accompanied by lots of new accessions often indicates gaps in reporting, as new accessions in should pull the average down. A descending blue line here indicates higher quality collection management; as the more checks are done the average comes down proportionally. The huge numbers of objects out since 2020 are reflective of better systems and a concerted effort to increase the quality of our collection management. Most of these plants did not die in these years; they were long dead but were not confirmed so in the database. The drop in average days prior to 2020 can be explained by ‘survivorship bias’–very high average days objects dropping out of the dataset and being replaced with zero days objects, altering the average significantly.

Year	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023	2024	2025	2026
Accessions	5215	7399	10134	10395	7032	6139	4488	5697	7150	10080	7591	8925	7047	11093	5105	4323	5097	4761	3005	3436	1150
Deaths	3166	4491	4072	10702	3762	3506	3874	3136	3277	3091	6045	4766	3851	4348	2716	14202	19220	16932	19344	17398	8281
Average days since last seen	5524	5645	5708	5731	5935	5842	5826	5955	6031	6121	6112	5809	5495	4926	4460	4383	3779	2903	2417	1747	1508

5.2 Pie of objects within inspection window or overdue

Finally, we set our inspection interval at 3 years as standard. This chart expresses as a percentage what proportion of our living collections are overdue for inspection.

References

Cano, Á., Powell, J., Aiello, A.S. et al. Insights from a century of data reveal global trends in ex situ living plant collections. Nat Ecol Evol 9, 214–224 (2025). https://doi.org/10.1038/s41559-024-02633-z

Report rendered on: 22 May 2026, 12:13 BST