Key Context

This report has been produced using Kew’s internal Operational Plan Review metrics and modified for Patricia Stadler’s Kew Diploma dissertation. 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 once marked ‘dead’ in the database is considered no longer present in the collection.
If that plant was the only individual of its species, then that species has also been lost.
Failure to update this ‘living status’ in collections are ‘Alive’ or ‘Dead’ inflates diversity metrics. The frequency of reporting can be thought of as ‘data health’.
Any change over time therefore must always be contextualised against data health.
Increasing data health over time can look like species loss
Where overinflation of collections data has occurred, it can take many years of improved collection management to correct.
This correction will look like losses from the collection on charts showing change over time.
Until data health is consistently high year on year, the true trends will be masked.

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	51	51	51	52	52	53	53	54	54	55	54	55	55	54	54	54	52	52	52	46	45
Taxa	57	58	59	60	60	61	60	61	62	63	62	63	63	62	62	62	60	57	57	51	50

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	51	51	51	52	52	53	53	54	54	55	54	55	55	54	54	54	52	52	52	46	45
Taxa	57	58	59	60	60	61	60	61	62	63	62	63	63	62	62	62	60	57	57	51	50
Genera	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	1	1	1
Families	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	1	1	1
Cultivated	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

2. Conservation Metrics

OPR Target: 3% increase year on year. 2024 actuals: 2025 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	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1

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	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1

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	0	0
Orders fulfilled	74	55	48	0	0

4. Wild Accession Metrics

OPR Target: >300 distinct accessions 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 2024 and 2025.

Year	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2019	2020	2025	2026
Accessions	1	3	3	13	4	1	4	10	4	15	27	1	7	2	7
Distinct accessions	1	1	3	7	3	1	2	6	3	11	22	1	6	2	7

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	47	51	55	90	83	121	25	182	138	73	189	284	53	52	51	0	0	0	0	0	14
Deaths	25	22	22	15	36	17	32	32	20	28	38	24	37	31	0	88	192	145	314	125	0
Average days since last seen	4576	4703	4932	4904	4891	4461	4798	4802	4928	5119	4964	4586	4703	5008	616	918	817	725	280	196	497

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: 06 March 2026, 07:22 GMT