What is the animal that looks like all animals? The locust, because it has the
horns of deer, the eyes of cows, the front of horses, the legs of storks, the
tail of snakes, and the wings of pigeons(Salido y Estrada, 1874: 69).
1. Introduction
Locust plagues are some of the oldest registered and recurrent insect outbreaks
that have forced people to act at various times, in several regions. There is a
strong cultural connotation associated with the locust invasions, which are
mentioned in a few religious texts (e.g. Kritsky, 1997; Aharoni, 1938; Curtis, 1883). Several studies were recently
published on these outbreaks (Sprenger, 2015; Deveson & Martinez, 2017; Gugliuzzo & Restifo, 2017; Loskutova & Fedotova, 2015; Deveson, 2011). Focusing on agricultural losses, studies
generally examine distribution, impacts, control measures and perceptions,
centering the analysis on a single country, which prevents the exploration of
the transnational dynamics regarding how the fight against locusts was carried
out1. These dynamics seem fundamental since locust surges affect several areas
which, in many cases, encompass several countries2.
The term “locust” refers to certain species of short-horned grasshoppers in the Acrididae family (Order Orthoptera) that may form a swarm. In a solitary phase, these insects are innocuous to the
field crops. However, their transformation from the solitary phase to the
gregarious phase results in the long or short-distanced migration –depending on the species– of dense populations and, consequently, agricultural damages. These two phases
were first suggested by Boris Uvarov in the 1920s (Uvarov, 1921, 1928). Further
research identified intermediate transient phases with morphological and
biometric characteristics that distinguish them from other phases and led to
the discovery of “permanent zones”, continuously occupied habitats where swarms were formed3. Although this phenomenon is not completely understood, studies suggest that
this transformation occurs under certain propitious climatic conditions and
adequate habitat. In the case of the Moroccan locust (Dociostaurus maroccanus) –the species that has been the subject of great concern from the Iberian
Peninsula scientific and political authorities– spring rainfall is critical, the optimum being approximately 100 mm. Two or
more consecutive years of spring precipitation deficit lead to changes in
vegetation cover (creating a characteristic mosaic pattern with patches of bare
soil and short, tufty grasses) making the habitat very favourable for the
species to flourish (Latchininsky, 1998).
Locust swarms have devastated crops and have been a contributory cause of
famine, threatening the economy and leading to human migrations. In 1916, the
International Institute of Agriculture4 published La lutte contre les sauterelles dans les divers pays. This book was an attempt to solv[e] a problem of vital importance to agriculture in several countries: the fight
against locusts (International Institute of Agriculture, 1916: V). The urgency of international
cooperation in the struggle against these insects was, then, asserted and
several international conferences were organised, throughout the twentieth
century, to discuss the subject (e.g. Buj, 1996: 165-238; Sistach, 2007: 197-202). Transnational collaboration was,
thus, considered fundamental.
The Iberian countries have a track record of locust invasions. Several Spanish
studies focused on historical outbreaks, analysing which areas had been
infested and what measures had been taken to fight locusts, as well as their
effectiveness5. Notwithstanding, Spanish historiography forgot the territorial continuity and
omitted what was happening in Portugal during the same period. Apart from a
brief chronology of locust outbreaks, in Portugal, these plagues have not yet
been analysed, neither from an economic, agricultural, and environmental
perspective, nor from a historical one (Silva, 1947). A general overview of
their geographical impact in both Iberian countries, as well as the measures
undertaken to extinguish this insect from the nineteenth century onwards, is
still to be made.
A global outlook might be particularly relevant to understand the Iberian
history of locust outbreaks, since there are no geographic or ecological
boundaries between Portugal and Spain to prevent the movement of animals
between them. In fact, these neighbouring countries share the same piece of
land, the Iberian Peninsula, surrounded by the Atlantic Ocean on its northern,
western and south-western coast, and by the Mediterranean Sea on the
south-eastern and eastern coast. Apart from the northern areas, climate is
characterised by dry summers and mild, moist winters. Some regions, especially
in central Spain, have an extremely low precipitation level and very hot
summers, bearing resemblance to desert or semi-arid climates. This continental
Mediterranean climate, together with the steppic ecosystems, is particularly
suitable for the development of locust outbreaks which, from time to time, rise
from the so-called “permanent zones” (unevenly distributed throughout the Peninsula), invading large areas
throughout the Iberian territory (Cañizo, 1942).
Although there are other locusts in the Iberian Peninsula that have occasionally
caused agricultural losses, the Moroccan locust, as already mentioned, was the
one causing major damages. On a global scale, it is still considered a major pest of many crops due to its voracity and for being a highly polyphagous species, harvesting all
main cereals (Latchininsky, 1998).
This paper aims at contributing to a better understanding of locust outbreaks in
the Iberian Peninsula. Taking the Portuguese case as a starting point, it
provides a comparative historical account of surges and the fight against them
in Portugal and Spain. It explores the historical geographical distribution of
the Moroccan locust invasions, with emphasis on the outbreaks that occurred
between 1898 and 1947. 1898 marks the first Portuguese responses at national
level and 1947, the year of the last major outbreak before preventive measures
started to be taken in Portugal. There are few records of outbreaks before and
after this timespan. Therefore, general aspects of legislative acts and control
measures issued before 1898 and until the present time will also be mentioned.
Firstly, the historical and geographical distribution of the Moroccan locust
invasions will be explored. Secondly, Portuguese and Spanish legislative acts
will be analysed, comparing the ways in which both countries addressed the
locust outbreaks in terms of logistical and administrative resources. Thirdly,
the control measures and other measures that have been taken on the ground,
throughout the years, will be described. Lastly, the paper will deal with
people’s perceptions regarding the locusts’ origin and the effectiveness of the measures taken against them.
The following research questions will be addressed: a) What areas were affected
by the locust outbreaks?; b) How did those outbreaks change over time?; c) Were
the control measures in Portugal and Spain similar?; d) Were Iberians fighting
the locusts together, as recommended by international institutions?; e) How was
the plague and the action of “neighbours” perceived?
By focusing on the Iberian case, this article ultimately aims to contribute to a
broader understanding of the measures implemented worldwide in the fight
against a cross-border bio-invader that threatened national and international
economies. Moreover, considering that the European Red List of Grasshoppers, Crickets and Bush-crickets has only very recently been published (Hochkirch et al., 2016) and in a context where a clear picture of the dynamics and regulation
of the grasshopper populations arises from an increased attention on long term
descriptive studies (Chapman & Joern, 1990: 466), this research also has the goal to promote better
understanding of change over the years. The main purpose of this analysis is
not to analyse the environmental impact of control measures or land use change –issues where IUCN recognised there are knowledge gaps (Hochkirch et al., 2016)– but to identify general trends and patterns of locust outbreaks and procedures
to contain them over time. The research intends to stimulate further research
which consider historical data, emphasising forgotten aspects of locusts’ life histories, contributing, thus, to the discussion about the factors that
led to the outbreaks’ decline, and providing a more informed context for future Orthoptera management programmes.
2. Sources and Methodology
This paper adopts a comparative approach, trying to find common strategies,
collaboration and potential coordination between Iberian countries. Sources
report locust outbreaks, their spread and the control measures taken to
mitigate impacts. Special attention was given to data reporting the historical
geographic distributions of the locust invasions. The information on the
occurrences was linked to geographical coordinates in a relational database and
analysed in a Geographic Information System.
Texts from Azcárate (1996) and Buj (1996) were crucial in the identification of the geography
of the invasions, and the understanding of the main responses to the locust
outbreaks throughout time in Spain. Mostly digitalised and freely accessible,
the nineteenth and twentieth century reports and agricultural publications also
constituted the support for an investigation which was intended to extend to
the entire Iberian area.
As far as Portugal is concerned, primary sources were analysed: legislation,
official regulations, technical reports and administrative documents, namely
the correspondence between local and regional institutions (such as civil
governors and municipal authorities) and national agencies of agriculture and
plant pathology. Newspaper articles were also an important source, used ad libitum for their useful insight into the popular perceptions of the locust outbreaks6. Moreover, newspapers report surges on a local and regional scale, dimensions
often not so noticeable in the official documents, allowing us to understand
how national policies were applied locally.
Some limitations were considered when drawing spatial references on maps at a
national and Iberian scale. Throughout the historical record, a few unevenly
distributed sources indicated precise locations which could be translated into
latitude-longitude coordinates. However, many sources only offered a general
impression of the territorial units where locusts were found (e.g. parish, municipality or district). The first were accurately marked through a
point on the map whereas the latter were converted from a polygon to a specific
location using their centroid. The references to locust invaded areas are
sometimes based on second-hand information or inexpert observations, for
instance, in local newspapers.
High resolution maps on the historical distribution in Portugal were created
based on those detailed primary sources. The Spanish sources already summarised
and compiled information, reporting more data on the affected provinces than on
localities, and giving greater attention to years of major outbreaks. Thus, to
compare the Portuguese and Spanish cases, the analysis was conducted at a
regional level, considering the districts (in Portugal) and the provinces (in
Spain) as equivalent administrative/territorial units7.
A few concepts and limitations should still be clarified. The Moroccan locust
goes through the egg, nymph and adult stages. The eggs are laid during summer
and remain in the soil until the following spring, when they hatch. New-born
nymphs undergo an incomplete metamorphosis, going through intermediate stages
until they reach the adult stage, which usually occurs in summer. Adults differ
from nymphs in their ability to fly. The Portuguese and Spanish terms
equivalent to “outbreaks”, “invasions” and “infestation” are used interchangeably, referring to a sudden increase in locust populations
due to migration or the hatching of eggs. Some sources did not refer the
specific designation of the species that caused the invasion. General terms
like “locusts” or “acridians” were frequently used instead of the correspondent scientific name. Although
there is a low risk of error since other species were less frequent and only
occurred profusely in very specific locations, in some rare cases, other
acridians might have been responsible for the invasions, and not the Moroccan
locust.
3. Spatial analysis of historical locust outbreaks
From the late nineteenth century to the mid-twentieth century there were several
locust infestations in the Iberian Peninsula which were considered a serious
agricultural problem. Figure 1 illustrates the 824 records of invasions,
between 1898 and 1947, mentioned in the sources analysed. Data was organised in
different categories according to distribution.
Figure 1
Provinces (Spain) and districts (Portugal) affected by locust outbreaks
by categories of frequency, 1898-1947
Source: see section 2 for method used for analysing the data here presented.
Figure 1 reveals no historical surges in the north or east of the peninsula or
only a few sporadic ones in Spanish provinces. The highest frequency of
repeated outbreaks was in the southern and south-western area of the peninsula.
Cáceres and Badajoz were the Spanish border provinces with more registered surges
from 1898 to 1947. Their neighbouring Portuguese districts, Castelo Branco and
Portalegre were in the same category of frequency.
In the 1940s, a Spanish research about the Moroccan locust and climate
identified three different areas in the Iberian Peninsula related to the
presence or absence of locusts (Cañizo, 1942). These included areas where locusts were not present; areas where
locusts were always present (called “permanent zones” or “reserves”) where, under certain climatic conditions, they became gregarious, starting
migrations to broader areas; and areas that could potentially be invaded by
migrating swarms. Contrary to that study, our data shows a historical invasion
area much larger than the one suggested at the time. In the Portuguese area
alone, we compiled 671 historical records of locust invasions. Portugal had a
large suitable area for locust outbreaks and invasions. In the 1940s, “permanent zones” were also identified by Portuguese entomologists and engineers8.
The detailed data from Portugal allowed for the study of the spatial impact of
locust outbreaks per year (Figure 2). Three major surges (MS) stood out: MS1,
from 1898 to 1905; MS2, from 1914 to 1922; and MS3, from 1943 to 1947. During
other periods, locust outbreaks affected one or two Portuguese districts: 1907
(Santarém and Portalegre); 1908-1910 (Portalegre); 1914 (Santarém); 1924 (Portalegre); 1934-1935 (Portalegre).
Figure 2
Number of districts affected by locust outbreaks in Portugal, 1898-1947. Three
major surges (MS) are revealed: MS1 (1898-1905); MS2 (1914-1922); MS3
(1943-1947)
Source: see section 2 for method used for analysing the data here presented.
The graph shows the existence of periods of increasing incidence in each MS
period, until a maximum number of affected districts is reached (MS1, nmax =
11; MS2, nmax = 8; MS3, nmax = 7), followed by a decrease. This evidence
suggests a self-regulating process. The increase results from a transformation
to the gregarious phase, followed by migrations, which could reach hundreds of
kilometres9. When locusts encounter unsuitable climatic conditions, or unsuitable habitats,
they tend to return to their solitary phase, reducing, thereby, the area of
invasion10. This pattern is similar to the one concerning the number of neighbouring
countries in which the Desert locust (Shistocerca gregaria) outbreaks were reported throughout several years (Chapman & Joern, 1990: 424-27). It is also like the pattern of other orthopteran
outbreaks, when considering the fluctuations in relative abundance over time
(Chapman & Joern, 1990: 424-27).
The Portalegre and Castelo Branco districts have always been subjected to locust
infestations, whereas other areas only had outbreaks in a specific period
(Figure 3). A brief description of each major surge complements the records of
occurrence drawn on the maps.
3.1. MS1 (1898-1905)
This well documented surge started in Spain and spread, reaching the
south-eastern area of the Faro district. The exact species was not identified
in 1898. Occasionally, harmless African locusts invaded this area and some
people thought that in 1898 this was the case. However, they were wrong, as
these insects were a different species. They had laid eggs on the soil which
led to a major outbreak the following spring.
To better understand the dimensions of the 1899’s invasion, only in the district of Faro (in the south of Portugal) 1,000 ton of
locusts was caught (Monteiro, 1900: 2), which is a tremendous number of
individual specimens as one kilogram of locusts contained about 14,931 insects
(Seabra, 1900: 36). In the same year, 60,000 eggs per square meter were found
(Dirección General de Agricultura, Minas y Montes, 1920: 7). Two years later, the numbers
were still staggering11.
National authorities reacted, adopting measures to contain the surge. Detailed
reports with information about the places where the locusts had laid their eggs
in every estate were written to destroy them before the following spring.
Meticulous maps of the district of Beja were drawn, pinpointing those areas and
displaying the route of the insect12.
Figure 3
Locations of locust outbreaks in Portugal:
1898-1905 (MS1), 1914-1922 (MS2), and 1943-1947 (MS3)
Source: see section 2 for method used for analysing the data here presented.
Despite control measures, the scourge did not diminish, and, in fact, it spread
from the south to the north. In 1901, it reached its maximum in terms of number
of infested districts (Figure 2). These locusts had different origins: the
hatching of eggs deposited by locusts in previous years and the successive
invasions coming from neighbouring areas. In fact, various swarms had arrived
in the country, through the border, crossing it at multiple points and at
various times. For instance, during 1901, locusts entered the district of
Castelo Branco, from Spain, at least two times, on June 6th and July 2nd. Portalegre was also invaded in late July, when locusts spread throughout the
district during the following c. 15 days. Simultaneously, Beja and Faro, which were already, as other districts,
fighting locusts born on Portuguese soil, were also struggling with new
invasions that were coming from the Spanish territory. As a flying species, it
was easy for the locusts to travel to numerous districts, namely Évora, Santarém, Leiria, Coimbra and even Viseu13. The situation seemed out of control. A fierce combat continued to be fought in
the following years.
By 1905, the locusts seemed to have been defeated, occurring only in Portalegre
and Castelo Branco, the most affected Portuguese districts during the entire
period studied, which bordered the Spanish province of Extremadura.
3.2. MS2 (1914-1922)
Locusts’ first appearance in 1914, in Santarém, seemed to have been controlled. However, their occurrence in 1915 in the
northern area of Portalegre was neglected, which probably led to their
reappearance in two more districts the following year (Silva, 1947: 31-2).
Fortunately, losses were not substantial in 1916, contrary to what happened in
1917, when, although the number of affected districts remained constant, the frightening march of acridians increased the invaded area. Spreading to the neighbouring municipalities still deemed undamaged,
threatening the destruction of future crops, this outbreak triggered political decisions about control measures14.
By 1918, the huge expansion of the invaded area made it clear that the fight was
far from over. Understanding the plague became crucial for its fight. Queries
were carried out to find, with exactitude, which places had been invaded, what
the specimens’ origin was and where the locusts had laid their eggs. Information about their
life cycle was considered fundamental: the month in which the eggs had hatched
and when the nymphs had passed to the winged state. Control measures were also
assessed: what means had been used to extinguish locusts and whether this
extinction had been complete or partial; how the workers had been paid (by day
or weight); and how the owners, renters or partners, municipal or
administrative authorities, military or agricultural associations had helped.
Locusts’ samples needed to be sent to the central Plant Pathology Laboratory (Laboratório de Patologia Vegetal) to be studied15.
Locusts came partly from previously laid out eggs, partly from swarms from
various origins and directions, destroying the legend that locusts always follow a fixed direction16. In 1919, the surge reached its peak (n = 8 districts). Information compiled
both in 1918 and 1919 led to the production of hand-made maps by district (Évora, Beja, Lisboa, Santarém, Portalegre and Castelo Branco), which sustained campaigns for locust
extinguishment in the following years17.
3.3. MS3 (1943-1947)
In the 1940s, at the beginning of the MS3 period, the right bank of the Tagus
River (Santarém district) was a fertile region for locust outbreaks. The most intensely
infested areas were in Pegões (Setúbal district) and Vendas Novas (Évora district). In the previous twenty years, those areas were dominated by
scrublands. The need to increase wheat cultivation led to a significant change
in land cover18. Landscape became a mosaic of cereals and fallow lands, which created the
propitious conditions for the multiplication of locusts and their transition to
the gregarious state. The drought of 1943 and 1944 accentuated those
conditions. As a result, in 1944, migratory swarms were formed, increasing the
area where eggs were laid and leading to a major outbreak in 1945, which became
even greater in 1946, since it was only fought in the final stage of locust
growth, when the insect was already flying19. An intense unprecedented campaign was then prepared. All have fulfilled their duty, even the pest, that died, without [...] causing sensuous harm in the year of 194620.
After 1947, occurrences in Portugal were scattered and less frequent. In 1949,
three locations from three different districts suffered from surges
(Portalegre, Setúbal and Lisboa). In the 1950s, invasions were rarely noticed: one in 1953 in
Lisboa district and two in Santarém district, in 1956 and 1957. There were no records of damages after the 1940s.
Meanwhile, locust outbreaks affected a wide area in Spain, particularly in
Extremadura, La Mancha and Andalucía, where there were favourable circumstances for their development such as the existence of
uncultivated or meadow lands, but also in León, Aragón and Cataluña (Planes, 1949: 175-76). By the end of the twentieth century, locusts were
still a concern in southern Spain, particularly in the regions of Extremadura
and Andalucía. The need to fight these species was still paramount: the average estimated
population of locusts in Extremadura in 1992 was 37,000 per hectare (Arias et al., 1993: 451).
4. Legislation regarding locusts
Outbreaks triggered local, regional and national responses, including mandatory
regulations, in both countries, throughout, at least, the last two centuries.
This section addresses the historical policies that concerned the fight against
locusts in Spain and Portugal. Each law or decree is not fully described but
the general trends and patterns in prescriptive measures are identified.
4.1. Spain
Spanish rules on how to proceed when locust pests occur exist, at least, since
1390. They have sought to, inter alia, solve the problem of financing control measures (Vázquez Lesmes & Santiago, 1993: 146). Over the centuries, procedures have been designed, namely
in 1755, when, after a major outbreak, an extensive joint action for the whole
affected territory was organised and detailed instructions on how to destroy
the insect in its diverse growth stages were published (Mas, 2001: 69-72; Azcárate, 1996: 41-7). During the nineteenth and twentieth centuries, these
instructions were, generally, accepted and put into practice (Azcárate, 1996: 31-130).
A turning point in Spanish legal framework occurred when the State agricultural
engineers became important agents in the pests’ control (Buj, 1996: 167-74). Spain approved a detailed law for locust
extinction (Ley de Extinción de la Langosta) on 10th January 1879, which stated these engineers were to take part in provincial
boards (juntas provinciales), had to confirm the existence of infested areas and inform the Board about the
insect’s state of development. They also had to be present in every anti-locust
campaign (Ministerio de Fomento, 1900). Nevertheless, locals still had to meet
their obligations and tasks. Landowners and settlers had to report the presence
of locusts if their estates were infested. The municipality, then, ought to
inform the civil governor, while it organised a Municipal Council of Extinction
(Junta Municipal de Extinción de la Langosta) (Article 1), which, among other things, would demand a list of infested areas
from landowners and settlers (Article 7). The civil governor, in turn, would
organise a Provincial Board (Junta Provincial de Extinción de la Langosta) and inform the Ministry of Agriculture (Article 3). Furthermore, each
landowner should fight the locusts himself or allow others to do so (Article
10). The Board would proceed with the destruction if the landowners refused to
do it (Article 10). Inhabitants from the age of 16 to 60 could be requested –with payment– to help the extinction services (Article 15). Budget came from taxes paid to
the municipality –to which, taxes from neighbouring towns could also be added (Article 18). Fines
were also imposed on landowners or settlers who did not declare infestation on
their lands or that, in any way, hampered the work of the Board (Articles 25,
26 and 27). This new law marked the strengthening of legislation, bringing the
technical-scientific skills of engineers (who then became state employees) to
the fight against this pest.
In the years that followed, several other legislative acts introduced
administrative changes, i.e. several central and provincial administration bodies responsible for
coordination tasks were created while others were extinguished (Dirección General de Agricultura, 1933: 5-15). However, the main guidelines were
maintained.
A general law against plant pests, which marked an important milestone in the
history of the phytopathology in Spain, was published in 1908. A significant
part of this diploma concerned the fight against two major problems: the
phylloxera (Articles 18 to 57) and the locusts (Articles 57 to 87). The latter
was considered a public calamity so, fighting locusts was a public responsibility21. This legal status mirrored the social and economic importance of the locust
pests on a national scale. However, despite the new strong wording, the general
claims regarding the organisational structure of the fight against the locusts
were similar to previous rules: guidelines were defined by the State and the
implementation of those guidelines was ensured by regional and local
authorities; the landowner or tenant, on his own account, was responsible for
the pest’s extinction; funds were mainly collected in the municipality; and two
extinguish campaigns were to be held each year, one in summer and another in
winter. For a long time, this law was Spain’s basic legal piece in the fight against locusts (Arias et al., 1993: 428, 449). Although its fundamental essence remained unaltered, on
different occasions, some minor legal precepts have been added to this
legislation, accommodating scientific and technical developments regarding the
fight against agricultural pests, in general, and locust plagues, in particular22. Legislative acts that have been continuously published until the present day
reveal how the issue remains relevant (Arias et al., 1993: 428-29)23.
4.2. Portugal
Until 1899, Portuguese governments reacted to specific plant pests in certain
places without any general policy. Specific regulations had been issued, for
example in the fight against the Coccus hesperidium in the Azores (1845 and 1849)24, in the fight against the Tortrix viridana (1893)25, against the chestnut disease (1886)26 and olive tree diseases (1887)27. Regarding locusts, since they had caused damages to agriculture on several
occasions, rural populations had already been mobilised to kill the insect and
take it into the city, as proof that the order had been executed (Silva, 1947:
12-7)28. The army was sometimes called to contain the cruel scourge (Silva, 1947: 12-7). In 1873-74 and 1875-76, the House of Representatives (Câmara dos Senhores Deputados) even approved the use of extraordinary funds for the extinction of locusts29.
The similarities exhibited by Spanish and Portuguese regulations adopted from
1879 to 1908 in the way services were organised, the responsibilities and the
establishment of obligations and sanctions, give us confidence to affirm that
acts issued in Spain seem to have inspired the Portuguese legislators. The
Decree of 23rd December 1899 is the first general regulation against plant pests in Portugal30. Vineyard pests and diseases, particularly phylloxera, had been, until then, a
main concern. However, other crops also suffered damages. It was necessary to
be watchful, to fend off diseases on their first assault before they could destroy crops. The Government should be able to establish, in the critical moment, the providences which, according to the
nature of the incipient evil, [were] more adequate and effective31. The Plant Pathology Laboratory, created by this legal text, was the official
body for the study of plant disease and plant parasites, and the establishment
of measures for the defence and treatment of crops (Article 15). The control
measures, however, should be implemented by multiple agents: landowners,
beneficial landowners, tenants, overseers, and beneficial holders, as well as
associations (e.g. agricultural unions) and local and regional authorities who managed land
(Articles 9 to 14). Accordingly, instructions on the methods and timing
suitable for the application of the measures were provided in an official
announcement (Articles 4 and 7), and landowners were obliged to apply control
measures or allow access to their lands (Articles 4 and 5). Penalties for
non-compliance were laid out (Articles 6, 7, 8 and 28) and the State could
replace the addressees if they did not comply with the obligations (Article 6).
In addition, fungicides, insecticides and their raw materials -–whose trade and distribution were also regulated– were exempt from import duties, if considered useful and necessary for the
development of national agriculture (Article 17).
The 1899 Portuguese decree on agricultural pests resembled the 1879 Spanish law
on locusts, although it was a set of generic provisions which could be applied
to any plant disease. In other words, the 1899 law was not designed
specifically to fight locusts. Detailed measures and regulations, concerning
specific pests, were to be published afterwards. Instructions indicating the
practical means of fighting locusts were, in fact, issued in May 1900
(Monteiro, 1900). The cursed ones32 gave no truce in the years that followed, which justified moving forward to
streamline fighting procedures. A regulation (Regulamento dos serviços de extinção dos acrídios) was adopted in 190233. Tasks were assigned to official bodies that shared the responsibility with all inhabitants from 18 to 50 years of age, Portuguese or foreign, who live[d] in the [affected] municipalities (Article 1). Killing locusts was, from then on, mandatory (Article 2), and the
fight should start immediately after the first invasion, using animals and instruments at their disposal according to instructions that ought to be provided by the Agricultural
Services or according to the well known traditional methods (Article 4). Landowners of non-invaded –but neighbouring– properties could be called upon to contribute with personnel to assist services
(Article 3). A system of fines was also established for offenders (Articles 6
to 11, 15 and 17 to 20). Landowners were to notify the councillor of their
respective parish as soon as swarms were detected. Then the councillor was to
communicate the infestation to the municipal administrator, so that the civil
governor was informed. He then notified the district’s agronomist, who was responsible for establishing the necessary measures
(Articles 20 to 23).
The fact that the whole community was involved seems, at first sight, a positive
aspect. However, a framework like that implied a complex chain of information
and action between multiple agents, which could increase the risk of failure.
In fact, the populations complained: despite the numerous technicians
responsible for the locusts’ extinction, they were not aware of the death of a single locust due to their
job (Anonymous, 1899).
The 1902 Regulation was not repealed in the following decades, despite the
various administrative reforms that took place over the years34. In 1949, agricultural engineers from the National Agronomic Station (Estação Agronómica Nacional) considered it outdated: no one care[d] to enforce or make others enforce it; and in the face of the biological
knowledge about locusts most of the provisions ha[d] no reason to be applied35. From the 1940s onwards, the new Portuguese legislation did not ever mention
locust outbreaks, events that seemed to have been forgotten, contrary to what
had happened on the other side of the border36.
5. Fighting the locustS
Fighting locusts in Spain and Portugal was a long and continuous process, which
was relatively well documented throughout time. Since the fight was similar in
both countries, the analysis of how legal procedures were implemented will be
discussed jointly.
Two major periods were distinguished according to the different types of
strategy used: 1) the reactive strategy (before the 1940s), which consisted of
collective campaigns for the destruction of insects and their postures; and 2)
the preventive strategy (after 1940s), which consisted in avoiding the plague’s occurrence.
5.1. Reactive measures (until 1940s)
The way reactive measures were applied remained unchanged for almost two
centuries in Spain (after 1755) and Portugal (after 1900). Measures can be
divided according to the time of year in which they were employed –winter or spring. Differences were essentially due to the different stages of
development of the insect which required different strategies of destruction. A
thorough knowledge of the locusts’ life cycle was, in fact, at the base of the adopted measures, which were
adapted to the insect’s diverse growth stages.
After the first swarms caused distress on the invaded areas during spring and
summer, eggs laid on the ground became a major concern. The most convenient
seasons for their destruction were autumn and winter: the work of one man, then, match[ed] the work of thirty men, afterwards37. At this stage different methods should be used: 1) ploughing or harrowing
lands where locust eggs had been laid; 2) feeding pigs on infested grounds; and
3) using hoes or any other instruments to dig the earth and then removing the
eggs by hand. Regardless of the methods used, ditches should be dug to bury the
eggs38.
The winter methods were still considered important in Portugal in 1919 (Ministério da Agricultura, 1919). In Spain, they were even mandatory to farmers who
wanted governmental aid. In 1934, for instance, the Agricultural Ministry
provided insecticides for spring anti-locust campaigns only to those who had
properly run the recommended winter measures (Dirección General de Agricultura, 1935: 173). Spanish agronomic services still
considered them crucial when a monitoring service was under preparation in the 1940s (Dirección General de Agricultura, 1954: 104). Thereafter, egg destruction campaigns
decreased over time as the methods to kill adults became more effective and the
preventive measures were introduced (Arias et al., 1993: 426).
Spring campaigns were to start as soon as the nymphs hatched. At this stage, any
livestock would be helpful in the destruction of the new-borns through
trampling. Workers were used to crush insects on the ground, forming a circle that takes all the stain or the possible part of it, which would narrow
and bramble to the centre, where they would beat and whip them with the
instruments they carry, as well as squeeze it, burn it or bury it, so that it
would not revive (Azcá́rate, 1996: 44)39. They wore leather or hemp soles, beat the floor with mallets and caught
insects with nets. Locusts were also picked up by hand40.
Similar measures were used to kill adult specimens, although they were less
efficient when the locusts reached this developmental stage because they could
fly, however, they could still work if applied at dawn, when the insects were
less active. Nets, traps or physical barriers could also be used to direct the
locusts’ flight into trenches, where they could be destroyed. Wild and domestic birds,
like turkeys and chickens, were considered as important as pigs in the
destruction of the adult locust41.
Mechanical methods, like the ones depicted, were broadly used until the
mid-twentieth century (e.g. Dirección General de Agricultura, 1933)42, although they only slightly restrained the spread and somewhat lessened the damage at the
expense of important sums (Pestana, 1901: 4). In spite of the general mobilisation in the invaded areas
and the destruction of immense amounts of these insects their absence on the fields was not noticeable […] seeming to everyone that the human forces [were] not enough to extinguish them, and that their devouring craving was such that
they even fell on the dead and devoured them (Anonymous, 1756)43.
Mechanical methods were maintained through several centuries. Chemical ones, on
the other hand, kept being changed from the late nineteenth century, according
to the latest research, which intended to develop industrial insecticides safer
for humans and domestic animals, as well as easier to apply, more effective,
selective and less expensive. Gasoline, soap emulsion and oil, soap and carbon
sulphide, creolin, arsenate compounds, fluosilicates, organochlorides or
organophosphates, were routinely used, being dispersed with the help of sprays
and baits (Buj, 1996; Dirección General de Agricultura, 1954: 69, 98-104)44. Industrial insecticides are now recognised as a threat to people’s health and biodiversity.
5.2. Preventive measures (after 1940s)
The fight against the locusts, not only in the Iberian Peninsula but all over
the world, underwent profound changes after the emergence of Boris Uvarov’s research about locust ecology in the 1920s45. If locusts could be killed in their permanent habitats, the spread of pests to
broader areas could be avoided. A new era could, thus, begin: an “era of prevention”, based on two distinct stages: 1) prospection; and, if necessary, 2)
elimination46.
In 1946, a Portuguese entomologist described Uvarov’s research and subsequent investigations in detail (Silva, 1946)47. His paper was the starting point for the devising of spring preventive
campaigns that lasted, at least, until the early 1980s: careful and repeated
measurements would, every year, give an idea of the phase which the Moroccan
locust was in, as well as the differences to the previous year. This could easily point the optimal opportunity for a small-scale action that
would cut off a trend which revealed a dangerous transformation to the
gregarious phase (Silva, 1946: 363). Biometric indexing allowed for the recognition of the
locust phases; i.e. the solitary, the gregarious and the transient phases have distinct dimensions.
The identification enabled the implementation of control measures that would
restrain the development of the insect to a complete gregarious phase, with all
the negative consequences which that entailed, ensuring the impossibility of large-scale outbreaks48.
From 1947 onwards, a permanent monitoring service was established. It contrasted
with the structures that had been in place since the end of the nineteenth
century to control locust outbreaks. In the following years, entomologists from
the National Agronomic Station (Estação Agronómica Nacional) travelled through Portugal prospecting for areas potentially suitable for the
development of locust populations into the gregarious phase. Specimens were
then collected and measured; indexes were calculated and compared49. Monitoring became a routine work that effectively allowed for the recognition of populations that could cause
agricultural damages in the subsequent years50. In these cases, insecticides were used to contain the increase of insects. In
1957, the Moroccan locust was considered a chronic evil that could only be fought with a continuous monitoring service51. These preventive measures, which were still being implemented in the early
1980s52, might have been crucial in the control of the Moroccan locust surges in
Portugal. Other factors, such as land cover change and the use of strong
insecticides, may also have contributed for decreasing their frequency. A 2009
research about the Portuguese saltopteran fauna did not find the Moroccan
locust (Schmidt, Martinho & Paiva, 2009), although its occurrence was confirmed years after (Pina et al., 2017). Regardless of their presence or absence in fields and natural habitats,
entomologists do not seem to remember how locusts were once an agricultural
pest (Serafim, 2017).
In Spain, favourable climatic conditions in the late 1930s, associated with the
fact that estates had ceased to be cultivated because of the civil war, led to
an extended outbreak, giving rise to several legislative acts. A massive
campaign to fight the locusts was developed in 1939, while a series of
investigations were initiated with the objective of preventing future outbreaks
(Arias et al., 1993: 427, 449; Dirección General de Agricultura, 1954: 98)53. In this context, a permanent defence service with exclusive and specialised
personnel was organised in order to identify outbreak areas and contain
migrations as the gregarious phase was beginning (Dirección General de Agricultura, 1947: 173)54. Anti-locust campaigns’ organisation, direction and execution, as defined in 1939, were, broadly
speaking, similar to how they are today (Arias et al., 1993: 427, 449). Government make insecticides available to landowners, free of
charge, that should start to be applied when the locusts are first seen and
until they reach the adult state; at the same time, regular visits by
technicians to the infested estates allow for the detection of infestations
that persist the procedures taken by the landowners and the consequent
introduction of additional measures, namely aerial applications (Arias et al., 1993: 429-31)55. These new vigilance policies, as well as the increase of cereals in cultivated
areas and the introduction of new insect control insecticides, changed the
Moroccan locust status (Buj, 1996: 310).This decline in the severity of the
attacks was linked, in the 1950s and 1960s, to the massive use of the HCH 25%
insecticide and from the late 1960s onwards, to the use of aerial insecticide
applications (Arias et al., 1993: 427)56. No major outbreaks have been recently recorded in Spain. Agronomical services
believe locusts will not have the character of public calamity again, being relegated –like any other [potentially] harmful species– to the category of latent plague; duly monitored they ceased to be a nightmare
for national agriculture (Dirección General de Agricultura, 1954: 104).
6. The neighbours’ fault: the inglorious struggle
In the 1870s, a swarm left Valle de Alcudia (Ciudad Real), one of the “permanent zones” in Spain, and flew to the neighbouring areas, bringing desolation and ruin. Populations have not ceased to work to contain the evil, avoiding being plunged in the
greatest misery (Rivas, 1888: 43). For this reason, the publication of the Ley de Extinción de la Langosta in 1879 was praised.
Despite the high expectations raised by this new law, it was poorly implemented,
being almost forgotten; there were no means to apply it. Extinguishing the
locusts required that local authorities and landholders coordinated actions and
made their own resources available to everyone (Rivas, 1888: 43-4). While
farmers who had lost their crops accepted the application of control methods on
their fields, the cattle breeders dissented from the established rules (Rivas,
1888: 47). Egg destruction during the winter implied the destruction of
pastures. Thus, many dehesa landowners concealed the magnitude of the invasion to avoid expenses and losses
(Rivas, 1888: 45). They remained silent as the dead (Rámon y Vidal, 1902: 11)57 and, as such, the public control measures were not efficient. This situation has
even led to popular riots against landowners who refuse to extinguish the
locusts (Anonymous, 1900).
Inaction happened with the connivance of the local boards (juntas locales). Political struggles and local rivalries limited the appliance of the law: some dehesas have been “cleared” without consulting the owners, and in others, […] no one dared to denounce it. Local boards, although in charge of extinguishing the plague, seemed committed
to religiously guard that seedbed of insects (Rivas, 1888: 51-2).
The situation remained problematic in 1900: farmers’ compensations were unbearable; pasture owners continued to oppose land
cleansing; local authorities were still not doing an effective winter campaign;
the deficient distribution of gasoline –necessary for the effective employment of the control measures– led to an unequal fight in different places (Ministerio de Agricultura,
Industria, Comercio y Obras Públicas, 1902: 59-60)58.
While the Spanish blamed each other for losses in their own businesses,
Portuguese rural populations, local authorities and technical experts blamed
the inaction of their Spanish neighbours as they observed locust swarms
frequently travelling across the border.
For instance, it was common knowledge that the 1898-1905 surge had started in
Spain59. For the Portuguese agronomists there was no doubt about this. Locusts in a
late growth stage kept flying in from Spain, which prevented the effectiveness
of the measures taken by the Portuguese.
While it is true that many of the locust plagues had their origins in Spain,
particularly because both the climatic and habitat conditions were more
suitable there, the Portuguese perception of the Spanish control actions did
not reflect the efforts carried out in the neighbouring country, despite a
certain ineffectiveness. The Portuguese ignored the treated area across the
border, commented that the subject was walking around [...] neglected (Anonymous, 1903) and lamented the fact that given the abandonment they were also victims (Anonymous, 1902a). In face of the numbness of [his] neighbours (Anonymous, 1902b), the affected populations thought the evil devourers of Spain marched in pursuit of [their] cultures. (Anonymous, 1902a) Such narratives could have been used to back up claims for
financial support or to justify the unsuccessful anti-locust campaigns, which,
as we have seen, only achieved their goals after the 1940s, although, with an
impact on other insects and on the biodiversity in general.
A widespread opinion, both in newspapers and in the reports of technicians,
throughout the twentieth century, was that Iberians should fight the locusts
together. However, cooperation and coordination were rare or non-existent. One
single record revealed some shared efforts between central authorities. In
1900, Portugal sent a fungus to Spain that was expected to kill locusts, the Empusa acridii60. Portugal had received that fungus from the Institute of Grahamstown in Cape
Colony (Pestana, 1901)61 and, taking into account that the majority of the Portuguese invasions had come
from the neighbouring country, the Portuguese government offered some samples
to Spain62: [t]here is no one who did not see favourably the Iberian union in that sense (Mastbaum, 1901: 117).
The fungus cultures were sent to Madrid, but an Iberian union for this cause
remained only a shared desire among Portuguese technicians and populations,
during the following decades. Locust reinvasions from Spain continued to be
mentioned, rendering the combat efforts almost useless (Ministerio de Agricultura, Industria, Comercio y Obras Públicas, 1901: 82)63. Even in 1949, when the scourge was already controlled in Portugal, an
understanding between the two countries, although crucial, was still missing64.
7. Final remarks: A dangerous path
Insects are potentially harmful to agriculture and can lead to famines and
economic losses. These threats were, in several occasions, enough to shape
agricultural practices and policy-making worldwide. In a context where locust
plagues in Portugal have been forgotten, historical research gives us a clear
picture of Orthoptera fauna and their evolution in the Iberian Peninsula.
A thorough knowledge of legislative acts approved until the mid-twentieth
century, allows an assessment of the continuous interest in locust control,
both in Portugal and Spain. Overall, governments deal with plant pests in two
different ways: 1) approving legal measures to prevent the infestation,
including protectionist measures which restrict the entry and circulation of
certain products; or 2) approving control programmes which intend to extinguish
the pest or at least contain its development. As far as locusts are concerned,
this latter mechanism was crucial. As in other countries, the Portuguese and
Spanish governments took a leading role in structuring the fight against this evil. However, if the influence of centralised directives was undeniable, the
process of implementing the measures also meant an organisational effort driven
by regional or local authorities and populations that, to kill the insect,
ought to organise a well-structured scheme where everyone had a role to play.
The 1879 Spanish law and its counterpart, the 1902 Portuguese law, were the
culmination of a continuous process that for several centuries was trying to
regulate the fight against locusts. Until the mid-twentieth century reactive
measures were approved; afterwards preventive measures took the lead. From the
late 1940s onward, Portugal and Spain, focused their attention on “permanent zones”. However, the ways in which each country fought the Moroccan locust seem to
have been quite different. Portugal paid attention to the transient phases,
preventing the locusts from reaching the gregarious phase; Spain –maybe due to the larger areas that had to be prospected– based its action on early-warnings of gregarious stages, preventing swarm
formation and subsequent damage to crops. Although it is hard to access with
precision the real impact of locusts on agriculture, the perception of its
impact has always been dramatic. Fear, even if not justified, seemed to have
influenced and legitimised the adoption of public control measures. The
legislative acts might not reflect the negative impact locusts had on the
Spanish and Portuguese economy since ancient times, however, they do reflect
the fear of locusts.
Irrespective of the measures taken by each country, the locusts were a common
problem –which should be tackled together– since locusts travel freely through the Iberian Peninsula. Similarities in
legislative acts, as well as references to each other’s outbreaks and researches, seem to support this idea of cooperation. Iberian
countries appear to have observed each other’s policies and trials. However, reports from Portuguese authorities, as well as
descriptions in newspapers, stated that there was a need for cooperation
between the Iberian governments to set in motion a common anti-locust
programme. Locusts frequently came to Portugal from Spain which rendered
inglorious the fight carried out by the Portuguese. Therefore, collaboration
was, in this context, considered crucial.
Historical data on locust pests’ occurrences clearly contradicts the assumption that those insects never caused
agricultural damages in Portugal. Furthermore, taking into account the pattern
revealed by our data (number of districts affected by locust outbreaks per
year) which suggest a self-regulation process, control measures taken before
the 1940s appear to have been palliative and not truly effective. The 1940s
Iberian anti-locust campaigns should, therefore, be taken into account when
evaluating Orthoptera populations and designing future management programmes. Insecticides seem,
thus, to have had a major impact in diminishing population densities, or at
least, to levels that prevent swarms’ formation65.
Nowadays, no one seems to remember the danger caused once by the Moroccan locust
in Portugal. In Spain, although there are still preventive campaigns being
conducted, no major surges have been recorded in the last fifty years and
locust populations may be diminishing according to the representative
organisation of BirdLife International in Spain66. Although Dociostaurus maroccanus is classified as Least Concern (LC) in the European Red List of Grasshoppers, Crickets and Bush-crickets, these regional trends in the Iberian Peninsula are alarming. Reasons for
outbreaks seeming cease are not obvious and further research is needed.
Research shows that the Iberian campaigns of the 1940s marked a turn-over in
the anti-locust struggle. Outbreaks have been controlled with localised
preventive actions. More effective in their reaction against the surge, they
probably led to a decrease in population densities. To clarify differences
found, at present time, in the Moroccan locust populations in Portugal and
Spain still more historical research is needed for having a better
understanding of long-term land use change, as well as having finer data on
historic climatic factors. In fact, IUCN considers that climate change and
agricultural land use intensification, along with the use of pesticide and
fertilizers, are major threats to Orthoptera species in Europe, affecting, consequently reptiles and birds that feed on them
(Hochkirch et al., 2016)67.
The history of the locust outbreaks might seem an irrelevant subject from the
point of view of agricultural losses in current European societies, where the
phenomenon has become sporadic and less intense. In fact, although the Iberians
have fought the Moroccan locust for centuries, now, it is no longer a major
concern for decision-makers, agricultural managers, farmers or the public.
However, the present situation in Portugal and Spain hides a history of
fruitless struggle, agricultural damages and large expenses, and there is no
real evidence that support the mainstream perception that outbreaks have
ceased.
Locust outbreaks are an odd subject for urbanites and a “non-there” phenomena for rural communities, which have been progressively forgetting about
it. This ecological memory is being erased by a very long sequence of years of
numbness. In a biological approach, numbness corresponds to the maintenance of
the species in its solitary phase, in the form of dispersed and harmless
grasshoppers. In a more cultural approach, numbness recalls people’s detachment by ignorance or lack of personal experience.
The risk of locust outbreaks is minimal, someone can argue. A non-action policy –no needs, no measures– was put into practice in Portugal. However, historical accounts clearly suggest
that prevention turned out to be a solution. Therefore, to stop prevention, in
any circumstance, is not recommended. Risk assessments are currently performed
to face invasive species all over the word, namely the Desert locust
(Latchininsky & Sivanpillai, 2010). Regarding the Moroccan locust in the Iberian Peninsula, the
potential risk of swarms’ formation should still be considered when designing agricultural management and
evaluating Orthoptera populations, both in plant pest control measures and in biodiversity
conservation programmes (Pina et al., 2017: 27).
What role can be expected of the environmental history of locust outbreaks in
this context? Questions on how historical research is useful and used in
environmental studies and policies have been continuously raised in the last
two decades, at least since the publication of The Uses of Environmental History (Cronon, 1993: 5). Cronon’s paper reminds us that our histories are to help change the world, to alert to subjects which are not eminent or urgent, almost non-existent, as
the locusts.
Despite difficulties in integrating historical observations in studies on
environment or natural sciences, this paper revealed new aspects, or forgotten
ones. By assembling a large amount of documentation and depicting it in graphs
and maps, a clear picture of the evolution of the acridians’ dynamics, in the Iberian Peninsula, throughout time, emerges. Furthermore, the
way people dealt with the locust plagues over time is crucial for the
understanding of the effectiveness of past measures and to further embark on an
effective fight in the future. At the same time this paper gave rise to a set
of questions that ecological research, per se, would not, usually, infer: Why is it hard to find Dociostaurus maroccanus in Portugal? Were the Portuguese anti-locust campaigns more effective? Are the
Spanish campaigns avoiding migrations to Portugal, leading to a decrease in the
Portuguese populations?
Locusts have the particularity of disappearing (or almost) and [thus] to be forgotten by populations, scientists and decision-makers (Doré & Barbier, 2015: 192). Although further research is still needed, this paper goes
against the trend and as once more highlighted how historical research can illuminate important changes in the structure and
function of ecosystems, as well as the ways people have documented, understood,
and attempted to manage those changes over time (Alagona et al., 2012). Neglecting the history of locusts in the Iberian Peninsula is a step
towards forgetting the presence of the species Dociostaurus maroccanus in the Peninsula, which can lead to the impoverishment of the entomological
fauna in fields and natural habitats. Furthermore, abandoning a culture of risk
prevention is a dangerous path from oblivion to the possible return of
catastrophic surges.
acknowledgement
This work was funded by FCT – the Portuguese Foundation for Science and Technology (UID/HIS/04209/2013,
UID/HIS/00286/2013 and IF/00222/2013/CP1166/ CT0001). This paper benefited
greatly from a discussion with Sílvia Pina. We also thank to the reviewers of Historia Agraria for their useful comments.
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NOTAS A PIE DE PÁGINA / FOOTNOTES
28.
There are records of help from the populations, for example, in 1746, 1756,
c.
1816 and 1876.
