Temporal trends in pollination of the Betulaceae family.
| Reference (publication date) | Region (number of sites) | Study period | Methodology | Trend identification technique | PIn (grains per cubic meter of air per decade and significance) | PSS (days per decade and significance) | PSD (days per decade and significance) |
|---|---|---|---|---|---|---|---|
| Betulaceae | |||||||
| [16] (2016) | N Italy (1) | 1990–2004 | Hirst-type | Linear regression | + (~1,400) | No trend | |
| [17] (2023) | Central Europe | 1951–2015 | Phenological observations | Linear regression | – | ||
| [18] (2014) | Europe (13) | 1990–2009 | Hirst-type | Linear regression | + (* in 2 out of 13 sites, ns in the other 11) | – (** in 3 of 8 sites, ns in the other 5) | + or – (* in 2 of 8 sites, ns in the other 5) |
| Betula | |||||||
| [16] (2016) | N Italy (1) | 1990–2004 | Hirst-type | Linear regression | + | – | Slightly + (1.3) |
| [17] (2023) | Central Europe | 1951–2015 | Phenological observations | Linear regression | – (1.9) | ||
| [19] (2022) | United Kingdom (6) | 1995–2020 | Hirst-type | Linear regression | + (*) | – (ns) at 5 of the 6 sites | |
| [20] (2010) | NW Italy (1) | 1981–2007 | Hirst-type | Linear regression | + (*) | – (10.0) | No trend |
| [21] (2020) | S Germany (1) | 1988–2018 | Hirst-type | Linear regression & least squares fit | Slightly + | – (~2) | – (0.7) |
| [22] (2019) | France (7) | 1987–2018 | Hirst-type | Linear & polynomial regression | + (209 to 1,263) | – until 2002, + thereafter | – almost everywhere (2.4 to 5.7) |
| [23] (2021) | Central Germany (4) | 1998–2017 | Hirst-type | Cochran-Armitage test for trend | Slightly + (ns) | ||
| [24] (2005) | Austria (2) | 1980–2001 | Hirst-type | Linear regression | + (~125 in valley area, ~350 at higher altitude) | – (4.0 in valley area, 7.3 at higher altitude) | |
| [25] (2018) | Brussels (1) | 1982–2015 | Hirst-type | Local regression method (LOESS) | + | ||
| [26] (2003) | Switzerland (1) | 1979–1999 | Hirst-type | Linear regression | Very slightly + (ns) | – (9.5; *) | No trend |
| [27] (2025) | Texas, USA (1) | 2009–2023 | Hirst-type | Least square regression | + (0.7; **) | ||
| [28] (2021) | Benelux (5) | 1981–2020 | Hirst-type | Linear regression | + in 4 sites of 5, but * in only 2 | – in all sites, but * in only 1 | – but variable and ns |
| [29] (1993) | London | 1961–1990 | Hirst-type | Linear regression | + (especially after 1975) | – | No trend (very strong inter-annual variation) |
| [30] (2014) | Catalonia (8) | 1994–2011 | Hirst-type | Linear regression + non-parametric test | Very slightly + (ns) | ||
| [31] (1998) | Basel (1) | 1969–1996 | Hirst-type | Linear regression | + (*) | No trend | |
| [32] (2000) | Basel (1) | 1969–1998 | Hirst-type | Linear regression | + (~1,700; *) | ||
| [33] (2008) | Basel (1) | 1969–2006 | Hirst-type | Linear regression | + (978; *) | – (~3.9, especially since the end of the 1970s; *) | – |
| [34] (2008) | Switzerland (3) | 1969–2007 | Hirst-type | Linear regression | + (from 1969 to 1990), then – in Basel | – (1.7 to 3.6) | |
| [35] (2021) | Basel (1) | 1969–2020 | Hirst-type | Linear regression | + (~190) | – (~1.9) | |
| [36] (2016) | Spain (12) | 1994–2013 | Hirst-type | Linear regression | + (ns, but ** in Ourense) | ||
| [37] (2021) | Basel (1) | 1969–2018 | Hirst-type | Linear regression | + (ns) | – (~2; *) | – (~0.74; ns) |
| [38] (2021) | Switzerland (14) | 1990–2020 | Hirst-type | Linear regression + LOESS | + (*) | No trend | |
| [39] (2024) | NW Spain (3) | 1995–2023 | Hirst-type | Linear regression + non-parametric test | + (*) | Slightly – | |
| [40] (2018) | Brussels (1) | 1982–2015 | Hirst-type | Linear regression + Mann-Kendall test | + (ns) | – (ns) | |
| [41] (2019) | Switzerland (6) | 1985–2014 | Hirst-type | Bayesian statistics | + but – in recent years in 4 of 6 sites | ||
| [42] (2011) | Germany (10) | 1988–2009 | Hirst-type | Linear regression + Mann-Kendall test | + in NE and S | Slightly + in S | |
| [43] (2024) | United Kingdom (2) | 1970–2021 | Hirst-type | Generalized additive model for time series | + | No trend | |
| [44] (2016) | Stockholm (1) | 1973–2013 | Hirst-type | Linear regression | + (~1,000; ns) | – (~3.7; ***) | No trend |
| [45] (2011) | S Poland (1) | 1991–2008 | Hirst-type | Linear regression | + (*) | No trend | |
| [46] (2002) | Denmark (2) | 1977–2000 | Hirst-type | Linear regression | + (~1,150 to ~2,000) | – (6.2, ** in Copenhagen; 5.2, ns in Viborg) | + (2.3, ns in Copenhagen; 6.1, ** in Viborg) |
| [47] (2021) | Bavaria (8) | 1989–2018 | Hirst-type | Linear regression | + (ns, but * in Munich) | – (*) | |
| [48] (2021) | Bavaria (28) | 1975–2100 | Hirst-type & modelling | Linear regression | + initially, then – in lowlands (< 800 m) and + in highlands | ||
| [49] (1995) | Europe (5) | 1976–1993 | Hirst-type | Linear regression | + (*** in Basel, London, and Leiden; ns in Vienna and Stockholm) | ||
| [50] (2003) | W Europe (5) | 1968–2001 (partly) | Hirst-type | Linear regression | + in the 5 sites (* in Leiden, ** in Derby) | ||
| [51] (2024) | NE Italy (20) | 2006–2022 | Hirst-type | Theil-Sen estimator | Very slightly + | No trend | + (4.3) |
| [52] (2021) | France (6) | 1987–2021 | Hirst-type | Variable | + (~440) | – until 2002, + thereafter | |
| [53] (2009) | Finland (1) | 1974–2004 | Hirst-type | Linear regression & smoothing | + (*) | – (4; *), especially during later years | No trend |
| [54] (2014) | USA (6) | 1994–2011 | Growing degree hour model | Linear regression | + in 3 sites, – in 2 sites; ns everywhere | – in 4 out of 6 sites, slightly + in the other 2; but in all cases ns | Generally – (up to ~10), but * only in Newark |
| [55] (2015) | USA (50) | 1994–2010 | Unspecified | Linear regression | + in 5 of the 9 regions (54.6 in the W); – in the S (47.2) | – in 59% of the 50 studied sites and in 7 of the 9 climate regions (1.5 to 8.8, * in all cases) | – (up to 8.1 in 4 of the 9 regions; * in S, SE, NE and NW) |
| [56] (2012) | Europe (97) | 1977–2009 (partially) | Hirst-type | Linear regression | + (***) | ||
| [57] (2020) | N & Central Italy (9) | 2000–2016 | Hirst-type | Non-parametric Mann-Kendall test | No trend | No trend | – |
| [58] (2020) | Basel (1) | 1969–2018 | Hirst-type | Linear regression | No trend | – (~2) | |
| [59] (2021) | Georgia, USA (1) | 1992–2018 | Rotorod | Linear regression | No trend | – (4.8) | + (3.5) |
| [60] (2025) | Lithuania (3) | 2005–2023 | Hirst-type | Linear regression + Mann-Kendall test | No trend | – (0.5 to 6; ns) | Slightly + (ns) |
| [61] (2021) | Austria (1) | 1993–2017 | Hirst-type | Linear regression | No trend | ||
| [62] (2025) | N Italy (1) | 1997–2023 | Hirst-type | Linear regression | – (ns) | + (13.5; ***) | – (9.3; **) |
| [63] (2024) | Switzerland | 1990–2023 | Hirst-type | Unspecified | – from 1990 to 2000, + from 2000 to 2015, then – again | No trend | |
| [64] (2016) | USA (9 regions) | 2000–2050 | Modelling | Unspecified | – in most climate regions in 2047–2050 compared to 2001–2004 | – in the NW, NE, & W | – in 8 of the 9 regions |
| [65] (2013) | Europe + USA (5) | 2000–2040 | Modelling | Bayesian analysis | + (~2,450 to 3,320) | – (~4.75 to 5) | |
| 2000–2060 | Modelling | Bayesian analysis | + (~2,570 to 3,920) | – (~3.3 to 3.5) | |||
| 2000s–2090s | Modelling | Unspecified | – (1.3) | ||||
| [66] (2001)[67] (2002) | Europe | 1969–1998 | Phenological observations | Unspecified | – (2.7; *) | ||
| [68] (2001) | Switzerland (1) | 1980–1997 | Hirst-type | Linear regression | – (10.6; *) | ||
| [69] (1997) | United Kingdom (3) | 1954–1995 | Hirst-type | Linear regression | – (~5) | ||
| [70] (2002) | Europe (6) | 1970–2000 | Hirst-type | Linear regression | – in Belgium (6.3, *), in Switzerland (~10 after 1986, *), in UK (8.4 after 1982); no trend in Turku; + in Kevo (~15); + in Vienna until 1984, – thereafter (~11) | ||
| [71] (2007) | Europe (10) | 1970–2004 | Hirst-type | Linear regression | Significantly – in Turku, Zürich, London, Vienna, and Brussels; slightly – in France; no trend in Poland; + in Kevo | ||
| [72] (2010) | Lithuania (3) | 1970–1999 | Hirst-type | Linear regression | – (~3 to 5; *) | ||
| [73] (2002) | W of the NL (1) | 1969–2000 | Hirst-type | Linear regression | – (3.1; *) | ||
| 2000s–2090s | Modelling | Unspecified | – (1.3) | ||||
| [74] (2025) | Iberian Peninsula (12) | 1994–2023 | Hirst-type | Linear regression | + (3.3) | ||
| [75] (2013) | Central and S United Kingdom (3) | 1970–2010 | Hirst-type | Linear regression + distance weighted smoothing technique | – in the 1980s and early 1990s, then + | ||
| [76] (2014) | Ireland | 1990s–2030s | Process-based phenological model | Linear regression | – (on average, 0.75, more in the NE than in the SW) | ||
| Corylus | |||||||
| [16] (2016) | N Italy (1) | 1990–2004 | Hirst-type | Linear regression | – | No trend | – (~14 to 15) |
| [17] (2023) | Central Europe | 1951–2015 | Phenological observations | Linear regression | – (3.1) | ||
| [23] (2021) | Central Germany (4) | 1998–2017 | Hirst-type | Cochran-Armitage test for trend | Sightly + (ns) | ||
| [24] (2005) | Austria, in valley area (1) | 1980–2001 | Hirst-type | Linear regression | + (~850) | – (8.1) | |
| [25] (2018) | Brussels (1) | 1982–2015 | Hirst-type | Local regression method (LOESS) | + | ||
| [26] (2003) | Switzerland (1) | 1979–1999 | Hirst-type | Linear regression | + (ns) | No trend | No trend |
| [28] (2021) | Benelux (5) | 1981–2020 | Hirst-type | Linear regression | + (* in 2 sites of 5) | – (* in 4 sites of 5) | No trend |
| [30] (2014) | Catalonia (8) | 1994–2011 | Hirst-type | Linear regression + non-parametric test | No trend | ||
| [31] (1998) | Basel (1) | 1969–1996 | Hirst-type | Linear regression | + (**) | – | |
| [32] (2000) | Basel (1) | 1969–1998 | Hirst-type | Linear regression | + (~450; *) | ||
| [35] (2021) | Basel (1) | 1969–2020 | Hirst-type | Linear regression | + (~240) | ||
| [37] (2021) | Basel (1) | 1969–2018 | Hirst-type | Linear regression | + (248; ***) | – (4.5; *) | + (3.5; *) |
| [38] (2021) | Switzerland (14) | 1990–2020 | Hirst-type | Linear regression + LOESS | + (985 to ~1,093; *) | – (*) | – (*) |
| [40] (2018) | Brussels (1) | 1982–2015 | Hirst-type | Linear regression + Mann-Kendall test | + (*) | – (ns) | |
| [41] (2019) | Switzerland (6) | 1985–2014 | Hirst-type | Bayesian statistics | + | ||
| [42] (2011) | Germany (10) | 1988–2009 | Hirst-type | Linear regression + Mann-Kendall test | + | Slightly + in S | |
| [44] (2016) | Stockholm (1) | 1973–2013 | Hirst-type | Linear regression | + (~24; **) | – (~5.1; ns) | – (2.1; ns) |
| [45] (2011) | S Poland (1) | 1991–2008 | Hirst-type | Linear regression | + (***) | No trend | |
| [51] (2024) | NE Italy (20) | 2001–2022 | Hirst-type | Theil-Sen estimator | + (1,089) | – (7.3) | No trend |
| [56] (2012) | Europe (97) | 1977–2009 (partially) | Hirst-type | Linear regression | + (***) | ||
| [57] (2020) | N & Central Italy (9) | 2000–2016 | Hirst-type | Non-parametric Mann-Kendall test | No trend | – | No trend |
| [58] (2020) | Basel (1) | 1969–2018 | Hirst-type | Linear regression | + (~300) | – (~5) | |
| [61] (2021) | Austria (1) | 1993–2017 | Hirst-type | Linear regression | No trend | ||
| [62] (2025) | N Italy (1) | 1997–2023 | Hirst-type | Linear regression | + (331; *) | – (4.7; *) | + 0.6 (*) |
| [63] (2024) | Switzerland | 1990–2023 | Hirst-type | Unspecified | + (~412) | – (~5) | |
| [81] (2007) | Thessaloniki (1) | 1987–2005 | Hirst-type | Linear regression | + (~120) | No trend | No trend |
| [82] (2024) | Rome (1) | 1997–2016 | Hirst-type | Linear regression | No trend | ||
| [83] (2002) | Central Italy (1) | 1982–2001 | Hirst-type | Linear regression | + (1.0; ns) | No trend | |
| Alnus | |||||||
| [16] (2016) | N Italy (1) | 1990–2004 | Hirst-type | Linear regression | – | Slightly – | – |
| [17] (2023) | Central Europe | 1951–2015 | Phenological observations | Linear regression | – (3.6) | ||
| [23] (2021) | Central Germany (4) | 1998–2017 | Hirst-type | Cochran-Armitage test for trend | No trend | ||
| [24] (2005) | Austria (2) | 1980–2001 | Hirst-type | Linear regression | + (~1,100 in valley area, ~3,000 at higher altitude) | – (4.7 in valley area, 6.0 at higher altitude) | |
| [25] (2018) | Brussels (1) | 1982–2015 | Hirst-type | Local regression method (LOESS) | + | ||
| [26] (2003) | Switzerland (1) | 1979–1999 | Hirst-type | Linear regression | + (*) | No trend | No trend |
| [28] (2021) | Benelux (5) | 1981–2020 | Hirst-type | Linear regression | + (*) in 4 sites of 5 | – in 3 sites of 5, but * in only 2 | + in 4 sites of 5, but * in only 1 |
| [32] (2000) | Basel (1) | 1969–1998 | Hirst-type | Linear regression | + (~1,100; *) | ||
| [37] (2021) | Basel (1) | 1969–2018 | Hirst-type | Linear regression | + (~480; **) | – (ns) | – (ns) |
| [38] (2021) | Switzerland (14) | 1990–2020 | Hirst-type | Linear regression + LOESS | – | ||
| [40] (2018) | Brussels (1) | 1982–2015 | Hirst-type | Linear regression + Mann-Kendall test | + (*) | – (ns) | |
| [42] (2011) | Germany (10) | 1988–2009 | Hirst-type | Linear regression + Mann-Kendall test | + in NE and S | – in NW (1.4) | + in NW |
| [44] (2016) | Stockholm (1) | 1973–2013 | Hirst-type | Linear regression | + (~30.5; ns) | – (~2.4; ns) | – (~1.1; ns) |
| [45] (2011) | S Poland (1) | 1991–2008 | Hirst-type | Linear regression | No trend | No trend | |
| [47] (2021) | Bavaria (8) | 1989–2018 | Hirst-type | Linear regression | + | – | |
| [51] (2024) | NE Italy (20) | 2006–2022 | Hirst-type | Theil-Sen estimator | + (326) | – (4.4) | No trend |
| [56] (2012) | Europe (97) | 1977–2009 (partially) | Hirst-type | Linear regression | + (***) | ||
| [57] (2020) | N & Central Italy (9) | 2000–2016 | Hirst-type | Linear regression + non-parametric Mann-Kendall test | + (*) | – (*) | |
| [60] (2025) | Lithuania (3) | 2005–2023 | Hirst-type | Linear regression + Mann-Kendall test | No trend | – (6.5 to 17; *) | No trend in Siauliai and Klaipeda, + (> 5.0) in Vilnius |
| [61] (2021) | Austria (1) | 1993–2017 | Hirst-type | Linear regression | No trend | ||
| [81] (2007) | Thessaloniki (1) | 1987–2005 | Hirst-type | Linear regression | + | No trend | No trend |
| [83] (2002) | Central Italy (1) | 1982–2001 | Hirst-type | Linear regression | + (2.0; ns) | No trend | |
| [84] (2023) | NW Spain (1) | 1993–2018 | Hirst-type | Linear regression | + (1,120; **) | + (ns) | + (ns) |
| [85] (2021) | Slovakia (1) | 2002–2019 | Hirst-type | Linear regression + Mann-Kendall test | + | – | |
| [86] (2020) | Andalusia (3) | 1994–2017 | Hirst-type | Linear regression | + (* in Granada, ns elsewhere) | + in Córdoba (*) and Málaga (**), ns in Granada | |
The grey backgrounds correspond to studies that have made projections about the future. +: trend towards increased pollen concentration (PIn), earlier onset of pollination (PSS), or longer pollen season (PSD); –: trend towards decreased pollen concentration (PIn), later onset of pollination (PSS), or shorter pollen season (PSD); *: p < 0.05; **: p < 0.01; ***: p < 0.001. PIn: pollen integral; PSS: pollen season start date; PSD: pollen season duration; N: north; ns: non-significant; NW: northwest; S: south; LOESS: locally estimated scatterplot smoothing; NE: northeast; W: west; SE: southeast; SW: southwest; NL: Netherlands.