Decline in farmland flora and fauna as of 1900

© Chris van Swaay.
Farmland flora and fauna in the Netherlands have gone through substantial changes over the past century. Since 1900, plants on arable fields have declined by 35 percent; grassland butterflies by 80 percent, and characteristic birds of open farmland by 85 percent. This is evident from new historical time series with several biodiversity indicators which have been calculated by Statistics Netherlands (CBS), Floron, Dutch Butterfly Conservation and the Dutch Centre for Field Ornithology.

Over the course of the 20th century, Dutch farmland has gone through unprecedented changes in terms of yield potential and land use. These developments have been well documented by CBS in agricultural statistics. At the same time, there have been significant changes in farmland biodiversity. For three major groups of species, the long-term trend has been quantified with the aid of new statistical analyses; for arable field plants this was partly based on previously untapped data. With the newly available time series, long-term developments in the flora and fauna diversity of Dutch farmland have become better documented than before. These results have been used, inter alia, for the third edition of the Dutch Living Planet Report (LPR) of the World Wildlife Fund.

CBS applies the so-called Living Planet Index (LPI) to describe trends in the Netherlands' flora and fauna per group of species (e.g. butterflies). With this index, the trends in populations of separate species are combined into a single trend for that particular group of plant or animal species. The LPI is an internationally accepted method [1 and 2] to identify changes in biodiversity. First, counts of each species in the first year of the time series are indexed at 100, after which counts in each following year are expressed as a percentage of this value. All species population trends weigh equally heavily in the LPI. A decline in the LPI means that more species tend to deteriorate than advance. Wherever data are unavailable, CBS uses the number of grids containing a particular species.

Significant decline in flora of arable fields over latter half 20th century

The distribution of flora on arable fields in the Netherlands, which is monitored based on 65 characteristic plant species, has declined by 35 percent since 1900. This means that the number of grid cells containing plant species that are characteristic for arable land (such as the cornflower and the long-headed poppy) has declined by this much. Any decline in the population per grid cell has not been taken into account; the actual decline is likely to be much greater. As of 1950 in particular, a strong decline has occurred in wild plants on arable fields. It is precisely this period which has brought the most significant changes in terms of cultivation area and crops: during the latter half of the 20th century, rye and oats were replaced by silage maize, which is used as fodder. Rye and oat plots feature a large variety of farmland plants, whereas only few species can survive on silage maize fields. Aside from crop switching, other factors affecting wild plant variety include seed purification, weed control, and more intensive land use.
However, not all arable field plants have declined. The switch to silage maize has also led to a significant increase in certain grassy plants, such as cockspur grass.
The distribution of arable field flora has remained virtually stable over the years 2001-2018, relative to the previous period.

Arable field flora (1900-1925 = 100)
 TrendTrend_2
1900-1925100.00{ "high": 100.0, "name": "1900-1925", "low": 100.0 }
1926-195097.71{ "high": 106.69, "name": "1926-1950", "low": 90.01 }
1976-200064.91{ "high": 70.1, "name": "1976-2000", "low": 60.34 }
2001-201865.81{ "high": 70.81, "name": "2001-2018", "low": 60.94 }
Source: CBS, Floron
The brackets indicate the 95% confidence intervals.


Grassland butterfly population down by over 80 percent

Unfertilised or poorly fertilised grassland forms the single most important habitat for 17 characteristic grassland butterfly species such as meadow brown, small heath and common blue. Between the end of the 19th century and 2017, this group of butterflies declined by at least 80 percent. Over this period, five different species increased while ten other species declined. Eight out of these ten grassland butterfly species declined severely and four even disappeared completely from the Dutch landscape: the Lulworth skipper, the red-underwing skipper, large blue and the marsh fritillary.
Due to agricultural intensification over the past century, unfertilised or poorly fertilised grassland has become a rarity. Nowadays, grassland butterflies are almost exclusively to be found on flowery dikes and parcel margins, i.e. those landscape elements which are of little relevance for agricultural production. Not much has changed in the distribution of grassland butterflies since 1990.

Grassland butterly populations (1890-1939 = 100)
 TrendTrend_2
1890-1939100.00{ "high": 130.37, "name": "1890-1939", "low": 76.74 }
1940-196066.19{ "high": 79.07, "name": "1940-1960", "low": 55.17 }
1961-197043.96{ "high": 54.07, "name": "1961-1970", "low": 35.89 }
1971-198028.87{ "high": 34.48, "name": "1971-1980", "low": 24.06 }
1981-199020.75{ "high": 23.34, "name": "1981-1990", "low": 18.36 }
1991-200016.99{ "high": 20.29, "name": "1991-2000", "low": 14.3 }
2001-201016.79{ "high": 19.89, "name": "2001-2010", "low": 14.16 }
2011-201719.34{ "high": 24.79, "name": "2011-2017", "low": 15.19 }
Source: CBS, Dutch Butterfly Conservation
The brackets indicate the 95% confidence intervals.

Farmland birds in decline as of 1900

The characteristic breeding birds of agricultural areas (meadow birds, birds of arable fields and farmyard and thicket birds) have declined in number since the beginning of the 20th century. These include 27 breeding bird species. Twenty out of the 27 have been in decline since 1900. Only a few species, including the European goldfinch, are more common nowadays than at the start of the 20th century.
The historical development varies among farmland birds, such as the lapwing and the black-tailed godwit, and farmyard and thicket birds such as the yellowhammer, European stonechat and European goldfinch. Birds with open farmland as their habitat (arable fields and grassland; 14 different species) first grew in number during the first half of the 20th century, followed by a steady decline after 1960 among all the species. Their populations are still marked by strong decline from 1990 onwards. The total decline in farmland breeding birds has amounted to 85 percent since around 1900.
As for farmyard and thicket birds (13 species), their decline began in the early 20th century and continued until around 1990. Their populations have remained stable on average since then. Altogether, this group has declined by 60 percent. These birds breed in hedges, hedgerow and bushes on farmers’ fields and around the farmyard.

Farmland bird populations (1990=100)
 Open farmland estimate (limited data)Open farmland estimate (more data)Open farmland observationOpen farmland trendMargin of error in open farmland trendFarmyard and thicket estimate (limited data)Farmyard and thicket estimate (more data)Farmyard and thicket observationFarmyard and thicket trendMargin of error in farmyard and thicket trend
1900{ "name": "1900" }{ "name": "1900" }
1901{ "name": "1901" }{ "name": "1901" }
1902{ "name": "1902" }{ "name": "1902" }
1903{ "name": "1903" }{ "name": "1903" }
1904{ "name": "1904" }{ "name": "1904" }
1905{ "name": "1905" }{ "name": "1905" }
1906{ "name": "1906" }{ "name": "1906" }
1907{ "name": "1907" }{ "name": "1907" }
1908{ "name": "1908" }{ "name": "1908" }
1909{ "name": "1909" }{ "name": "1909" }
1910{ "name": "1910" }{ "name": "1910" }
1911{ "name": "1911" }{ "name": "1911" }
1912{ "name": "1912" }{ "name": "1912" }
1913{ "name": "1913" }{ "name": "1913" }
1914{ "name": "1914" }{ "name": "1914" }
1915195{ "name": "1915" }244{ "name": "1915" }
1916{ "name": "1916" }{ "name": "1916" }
1917{ "name": "1917" }{ "name": "1917" }
1918{ "name": "1918" }{ "name": "1918" }
1919{ "name": "1919" }{ "name": "1919" }
1920{ "name": "1920" }{ "name": "1920" }
1921{ "name": "1921" }{ "name": "1921" }
1922{ "name": "1922" }{ "name": "1922" }
1923{ "name": "1923" }{ "name": "1923" }
1924{ "name": "1924" }{ "name": "1924" }
1925{ "name": "1925" }{ "name": "1925" }
1926{ "name": "1926" }{ "name": "1926" }
1927{ "name": "1927" }{ "name": "1927" }
1928{ "name": "1928" }{ "name": "1928" }
1929{ "name": "1929" }{ "name": "1929" }
1930{ "name": "1930" }{ "name": "1930" }
1931{ "name": "1931" }{ "name": "1931" }
1932{ "name": "1932" }{ "name": "1932" }
1933{ "name": "1933" }{ "name": "1933" }
1934{ "name": "1934" }{ "name": "1934" }
1935{ "name": "1935" }{ "name": "1935" }
1936{ "name": "1936" }{ "name": "1936" }
1937{ "name": "1937" }{ "name": "1937" }
1938{ "name": "1938" }{ "name": "1938" }
1939{ "name": "1939" }{ "name": "1939" }
1940{ "name": "1940" }{ "name": "1940" }
1941{ "name": "1941" }{ "name": "1941" }
1942{ "name": "1942" }{ "name": "1942" }
1943{ "name": "1943" }{ "name": "1943" }
1944{ "name": "1944" }{ "name": "1944" }
1945{ "name": "1945" }{ "name": "1945" }
1946{ "name": "1946" }{ "name": "1946" }
1947{ "name": "1947" }{ "name": "1947" }
1948{ "name": "1948" }{ "name": "1948" }
1949{ "name": "1949" }{ "name": "1949" }
1950227{ "name": "1950" }170{ "name": "1950" }
1951{ "name": "1951" }{ "name": "1951" }
1952{ "name": "1952" }{ "name": "1952" }
1953{ "name": "1953" }{ "name": "1953" }
1954{ "name": "1954" }{ "name": "1954" }
1955{ "name": "1955" }{ "name": "1955" }
1956{ "name": "1956" }{ "name": "1956" }
1957{ "name": "1957" }{ "name": "1957" }
1958{ "name": "1958" }{ "name": "1958" }
1959{ "name": "1959" }{ "name": "1959" }
1960217{ "name": "1960" }140{ "name": "1960" }
1961209{ "name": "1961" }133{ "name": "1961" }
1962208{ "name": "1962" }129{ "name": "1962" }
1963215{ "name": "1963" }120{ "name": "1963" }
1964216{ "name": "1964" }116{ "name": "1964" }
1965210{ "name": "1965" }113{ "name": "1965" }
1966209{ "name": "1966" }102{ "name": "1966" }
1967204{ "name": "1967" }99{ "name": "1967" }
1968204{ "name": "1968" }98{ "name": "1968" }
1969191{ "name": "1969" }103{ "name": "1969" }
1970194{ "name": "1970" }109{ "name": "1970" }
1971184{ "name": "1971" }105{ "name": "1971" }
1972183{ "name": "1972" }113{ "name": "1972" }
1973168{ "name": "1973" }112{ "name": "1973" }
1974146{ "name": "1974" }107{ "name": "1974" }
1975148{ "name": "1975" }110{ "name": "1975" }
1976147{ "name": "1976" }105{ "name": "1976" }
1977154{ "name": "1977" }108{ "name": "1977" }
1978173{ "name": "1978" }102{ "name": "1978" }
1979167{ "name": "1979" }88{ "name": "1979" }
1980151{ "name": "1980" }92{ "name": "1980" }
1981153{ "name": "1981" }90{ "name": "1981" }
1982144{ "name": "1982" }97{ "name": "1982" }
1983140{ "name": "1983" }96{ "name": "1983" }
1984135{ "name": "1984" }89{ "name": "1984" }
1985124{ "name": "1985" }79{ "name": "1985" }
1986114{ "name": "1986" }77{ "name": "1986" }
1987111{ "name": "1987" }80{ "name": "1987" }
1988108{ "name": "1988" }86{ "name": "1988" }
1989124{ "name": "1989" }92{ "name": "1989" }
1990107100{ "high": 106.0, "name": "1990", "low": 95.0 }102100{ "high": 110.0, "name": "1990", "low": 91.0 }
19919198{ "high": 103.0, "name": "1991", "low": 93.0 }99101{ "high": 109.0, "name": "1991", "low": 94.0 }
19929595{ "high": 99.0, "name": "1992", "low": 92.0 }101102{ "high": 109.0, "name": "1992", "low": 97.0 }
19939393{ "high": 96.0, "name": "1993", "low": 89.0 }107103{ "high": 109.0, "name": "1993", "low": 98.0 }
19949190{ "high": 93.0, "name": "1994", "low": 87.0 }100104{ "high": 109.0, "name": "1994", "low": 99.0 }
19958487{ "high": 90.0, "name": "1995", "low": 84.0 }106105{ "high": 110.0, "name": "1995", "low": 100.0 }
19967684{ "high": 86.0, "name": "1996", "low": 81.0 }106105{ "high": 111.0, "name": "1996", "low": 100.0 }
19978581{ "high": 84.0, "name": "1997", "low": 78.0 }107106{ "high": 112.0, "name": "1997", "low": 101.0 }
19988278{ "high": 81.0, "name": "1998", "low": 75.0 }107106{ "high": 112.0, "name": "1998", "low": 101.0 }
19997375{ "high": 77.0, "name": "1999", "low": 72.0 }110106{ "high": 112.0, "name": "1999", "low": 101.0 }
20007371{ "high": 74.0, "name": "2000", "low": 69.0 }107107{ "high": 113.0, "name": "2000", "low": 101.0 }
20016868{ "high": 71.0, "name": "2001", "low": 65.0 }105107{ "high": 113.0, "name": "2001", "low": 101.0 }
20026364{ "high": 67.0, "name": "2002", "low": 62.0 }103107{ "high": 113.0, "name": "2002", "low": 102.0 }
20035860{ "high": 62.0, "name": "2003", "low": 57.0 }107107{ "high": 113.0, "name": "2003", "low": 102.0 }
20045956{ "high": 59.0, "name": "2004", "low": 54.0 }109107{ "high": 113.0, "name": "2004", "low": 102.0 }
20055853{ "high": 55.0, "name": "2005", "low": 51.0 }109107{ "high": 113.0, "name": "2005", "low": 102.0 }
20064750{ "high": 52.0, "name": "2006", "low": 47.0 }108108{ "high": 113.0, "name": "2006", "low": 102.0 }
20074447{ "high": 49.0, "name": "2007", "low": 45.0 }110108{ "high": 115.0, "name": "2007", "low": 102.0 }
20084445{ "high": 47.0, "name": "2008", "low": 43.0 }109108{ "high": 115.0, "name": "2008", "low": 102.0 }
20094143{ "high": 45.0, "name": "2009", "low": 41.0 }106107{ "high": 113.0, "name": "2009", "low": 102.0 }
20103841{ "high": 43.0, "name": "2010", "low": 40.0 }101107{ "high": 113.0, "name": "2010", "low": 102.0 }
20114940{ "high": 42.0, "name": "2011", "low": 38.0 }109107{ "high": 113.0, "name": "2011", "low": 102.0 }
20123938{ "high": 40.0, "name": "2012", "low": 37.0 }111106{ "high": 112.0, "name": "2012", "low": 101.0 }
20133537{ "high": 38.0, "name": "2013", "low": 36.0 }98105{ "high": 111.0, "name": "2013", "low": 101.0 }
20143736{ "high": 37.0, "name": "2014", "low": 35.0 }105104{ "high": 110.0, "name": "2014", "low": 100.0 }
20153635{ "high": 36.0, "name": "2015", "low": 34.0 }109103{ "high": 109.0, "name": "2015", "low": 99.0 }
20163534{ "high": 35.0, "name": "2016", "low": 33.0 }108102{ "high": 108.0, "name": "2016", "low": 97.0 }
20173333{ "high": 34.0, "name": "2017", "low": 32.0 }100100{ "high": 107.0, "name": "2017", "low": 94.0 }
20183032{ "high": 33.0, "name": "2018", "low": 30.0 }9398{ "high": 106.0, "name": "2018", "low": 91.0 }
2019{ "name": "2019" }{ "name": "2019" }
2020{ "name": "2020" }{ "name": "2020" }
Source: CBS, Sovon
The margins of error are 95% confidence intervals.

Sources