Growing (Corlett 2016). The abundance and distribution areas

Growing human pressure and climate
change are expected to have a major impact on biodiversity at a global scale (Segan
et al. 2016; Bellard et
al. 2015; Mantyka-Pringle et al. 2015; Hooper et al. 2012). The most important
factors threatening plant diversity are habitat loss, fragmentation and
degradation, overexploitation, invasive species, nitrogen deposition and
athropogenic climate change (Corlett 2016). The abundance and distribution
areas of many plant species are in decline under the pressure of these negative
factors (Van Landuyt et al. 2008; Kull et al. 2002).

Historical recordings can be very
useful tools to study plant distribution trends. Many European countries have
summarised their floristic studies in national grid atlases, e.g. atlases of
the British Isles (Perring &
Walter 1962; Preston et al. 2002), Germany (Haeupler & Schönfelder 1988; Benkert et al. 1996; Bettinger et
al. 2014), the Netherlands (Mennema et al. 1980–1985), Switzerland (Welten and
Sutter 1982), Poland (Zajac &
Zajac 2001), Denmark (Hartvig & Vestergaard 2015), etc. Some countries maintain
large electronic floristic databases such as Kasviatlas in Finland (Lampinen & Lahti 2013), Flora Danica
in Denmark (Bruun Asmussen Lange & Hermann 2016), FLORAWEB in Germany (Bundesamt
für Naturschutz 2018), etc. However, in many European countries
systematic floristic mapping started only after the Atlas Florae Europaeae
project was launched in 1965 (Uotila 2017; Niklfeld 1997). First national
distribution atlases of several countries (e.g. Hungary, Albania) have
therefore been published quite recently (Barina et al. 2017, Bartha
et al. 2015). In several countries where the floristic richness is the highest in
Europe (e.g. Spain, Greece) the atlases are not yet fully available (Real Jardin Botanico CSIC 2018; Strid & Tan 2017).

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Due to the lack of good historical
recordings, little information on distribution changes of vascular plants at
national scales can be found in scientific literature. Only a few countries
like Great Britain and the Netherlands have a long history of floristic
recording covering the whole national territory. Changes in the British and
Dutch floras in the 20th century have been analysed in a number of publications
(Doxford &
Freckleton 2012; Tamis  et al.
2005; McCollin et al. 2000). Local or regional floristic losses have also been
documented in other European countries (McCollin & Geraghty 2015; Wörz
& Thiv 2015; Van
Landuyt et al. 2008, Calster et al. 2008; Lavergne et al 2005; Van der Veken et al.
2005).

Floristic recordings in Estonia

The first vegetation mapping project
in Estonia was launched in 1934. The presence of plant species was recorded in
6` x 12` (approximately 114 km2) grid squares. Based on the records
collected in 1930-1950s, first distribution maps of Estonian vascular plants
were published in „Eesti NSV floora” Flora of the Estonian SSR (Zooloogia ja Botaanika Instituut & Eesti NSV Teaduste
Akadeemia 1953-1984) but only for less than half of the taxa (Kukk & Kull 2005).

The next period of floristic mapping
was started in 1973 by the Institute of Zoology and Botany. Estonia switched
to  6` x 10` (approximately 100 km2)
grid system used in most European countries. The results were summarized in the
atlas of the Estonian flora published in 2005 (Kukk & Kull 2005). The atlas presents distribution maps of
most native and widely spread naturalised alien species (1350 species in
total). The maps indicated that the distribution of a number of plant species
had decreased significantly (Kukk & Kull 2005).

Pärandkoosluste Kaitse Ühing and
Estonian University of Life Sciences are currently preparing a  new distribution atlas of Estonia. The field
recordings started in 2015-2016 and to a lesser extent continued in  2017. The new dataset based on these
recordings contains 1663 taxons. More attention has been paid to unsufficiently
studied families and genuses (such as Alchemilla,
Anthyllis, Taracaxum, Salix, etc), ruderals, aquatic and bog plants,
naturalised and invasive species (Pärandkoosluste Kaitse Ühing 2018).

The analysis of field recordings is
yet to be done but the current dataset has already shown that many introduced
plant species (e.g. Acer negundo, Primula elatior, Veronica persica, etc) have
expanded their distribution areas in Estonia considerably while some native
species (e.g. Urtica urens, Nardus
stricta) are far less widespread than expected by botanists
(Pärandkoosluste Kaitse Ühing 2018).

Although Estonia is one of the
countries with impressively long history of systematic botanical recordings,
the list of publications on changes in the Estonian flora is quite limited. A
comparative analysis of decline in ranges of plant species in Estonia and the
UK was published in 2015. The article demonstrated that the mean range size of
native plant species had declined 24% in Estonia between 1970-2004 and only 1/3
of species had maintained over 90% of their distribution area (Laanisto et al.
2015). Another study revealed that the mean decline in distribution range was
25% for Estonian orchid species in 1970-2004 (Kull & Hutchings 2006). These 2 studies confirm that
there has been a widespread loss of distribution areas of both common
and rare plant species in Estonia.

 

Margin species in the Estonian flora

Due to Estonia’s geographic and
climatic complexity, a very high per cent of vascular plant species reach the
margin of their distribution area in Estonia. The first list of margin species
in the Estonian flora was compiled in 1987 by Kask and Laasimer, it comprised
305 species (Kask & Laasimer 1987). Taxa with insufficiently studied status
or distribution area were excluded. An updated list of margin species was
published in 1999 by T. Kukk based on the results of extensive field recordings
in Estonia in 1970-1990s and new distribution information in the European plant
atlases (Jalas et al. 1996; Hultén & Fries 1986; Jalas & Suominen
1972–1994). The list contained 538 species (35% of the native flora) (Kukk
1999).

69% of
Estonian margin species are rare species (Kull et al. 2002). It can be
explained by the fact that environmental conditions are less favourable at the
range margin, species grow at their ecological minimum and have a weak
competition ability (Kask & Laasimer 1987). We can expect that under the
conditions of growing human impact and climate change, the persistence of
margin species have been lower than the average persistence of plant species.

 

An explanation how project data will be managed

 

Plant data from field recordings will
be stored at the PlutoF database managed by the University of Tartu Natural
History Museum. The dataset contains the following information: taxon name,
number of specimens observed, locality information (UTM grid or GPS
coordinates, the latter being available mostly for endangered species), habitat
type, name of the observer, observation date, additional information (if
available). The information is available for all registered users of the
database. Access to exact location information of I and II category endangered
species protected by law is restricted.

 

The
results of the atlas project will be made publicly available in an electronic atlas.
The e-atlas will indicate the presence of
species on maps in 100 km2 grid squares, exact location within the
grid squares or information on the abundance of species in each grid square
will not be presented.

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